Method for processing rrc message in relay node, and device for same

ABSTRACT

Provided are a connection control method and device based on integrated access and backhaul (IAB) using 5G NR wireless communication technology. The method of a relay node for processing an RRC message may include: setting a donor base station with a signaling radio bearer or a higher layer protocol connection; receiving an RRC message transmitted from a terminal; and transmitting the RRC message to the donor base station or another relay node using the signaling radio bearer or a higher layer protocol.

TECHNICAL FIELD

The disclosure relates to a connection control method and device basedon integrated access and backhaul (IAB) using 5G NR wirelesscommunication technology.

BACKGROUND ART

In wireless communication systems, relay technology has been adopted toexpand cell coverage using additional network nodes.

Thus, typical relay technology adopting LTE technology supports datatransfer at the IP packet level of the relay node and is configured toallow only one relay node to transfer IP packets between the UE and thebase station.

In other words, typical relay technology adopting LTE technologyprovides only a single hop relay function to provide simple services,and most of the configuration is made via static operations,administration, and management (OAM). Thus, the typical art is unable toconfigure a plurality of hop relays.

Upon attempting to support multiple hop relays via the typical LTEtechnology, it is impossible to separately process data via a pluralityof relay nodes, and over-IP layer signaling and data processing mayincrease latency.

Therefore, there is a demand for research on various protocol structuresto meet the quality of each service in multiple hops.

DETAILED DESCRIPTION OF THE INVENTION Technical Problem

In the above-described background, according to an embodiment of thedisclosure, a relay structure is provided for effectively distinguishingand processing data according to the requirements per UE or per servicewhen a plurality of relay hops are configured.

Further, according to an embodiment, an RRC message processing method isprovided for relaying an RRC message via one or more hops whilemaintaining the security between the UE and the base station in amulti-hop relay structure.

Technical Solution

According to an embodiment, a method may be provided for processing anRRC message by a relay node. The method may include configuring asignaling radio bearer or a higher layer protocol connection with adonor base station; receiving an RRC message transmitted from a userequipment (UE) and transmitting the RRC message to the donor basestation or another relay node using the signaling radio bearer or thehigher layer protocol.

According to an embodiment, a relay node may be provided for processingan RRC message. The relay node may include a controller configuring asignaling radio bearer or a higher layer protocol connection with adonor base station, a receiver receiving an RRC message transmitted froma UE, and a transmitter transmitting the RRC message to the donor basestation or another relay node using the signaling radio bearer or thehigher layer protocol.

Advantageous Effects

According to the embodiments of the present disclosure, a plurality ofrelay hops may be dynamically configured, and data may be effectivelydistinguished and processed based on the requirements for each UE or foreach service.

According to the embodiments of the present disclosure, delays in dataprocessing and over-IP layer signaling may be prevented whilemaintaining the security of the RRC message transferred in a relaystructure.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a view schematically illustrating an NR wireless communicationsystem in accordance with embodiments of the present disclosure;

FIG. 2 is a view schematically illustrating a frame structure in an NRsystem in accordance with embodiments of the present disclosure.

FIG. 3 is a view for explaining resource grids supported by a radioaccess technology in accordance with embodiments of the presentdisclosure;

FIG. 4 is a view for explaining bandwidth parts supported by a radioaccess technology in accordance with embodiments of the presentdisclosure;

FIG. 5 is a view illustrating an example of a synchronization signalblock in a radio access technology in accordance with embodiments of thepresent disclosure;

FIG. 6 is a signal diagram for explaining a random access procedure in aradio access technology in accordance with embodiments of the presentdisclosure;

FIG. 7 is a view illustrating an exemplary relay-based user planeprotocol structure in LTE technology;

FIGS. 8A and 8B are views illustrating a relay node (RN) startupprocedure in LTE technology;

FIG. 9 is a view illustrating an RRC connection configuration procedureusing a relay node according to an embodiment;

FIG. 10 is a flowchart illustrating the operation of transferring an RRCmessage by a relay node according to an embodiment;

FIG. 11 is a view illustrating an exemplary protocol structure fortransferring an RRC message according to an embodiment;

FIG. 12 is a signal flow chart illustrating a procedure for transferringan RRC message to a base station according to an embodiment;

FIG. 13 is a flowchart illustrating the operation of transferring uplinkuser data by a relay node according to an embodiment;

FIG. 14 is a view illustrating an exemplary protocol structure fortransmitting uplink user data according to an embodiment;

FIG. 15 is a view illustrating an exemplary protocol structure fortransferring uplink user data from a single-structure donor base stationaccording to an embodiment;

FIG. 16 is a view illustrating an exemplary protocol structure fortransmitting uplink user data according to an embodiment;

FIG. 17 is a view illustrating an exemplary protocol structure fortransmitting uplink user data according to an embodiment;

FIG. 18 is a view illustrating an exemplary protocol structure fortransmitting uplink user data according to an embodiment;

FIG. 19 is a view illustrating an exemplary protocol structure fortransmitting uplink user data according to an embodiment; and

FIG. 20 is a block diagram illustrating a relay node according to anembodiment.

MODE FOR CARRYING OUT THE INVENTION

Hereinafter, embodiments of the disclosure are described in detail withreference to the accompanying drawings. The same or substantially thesame reference denotations are used to refer to the same orsubstantially the same elements throughout the specification and thedrawings. When determined to make the subject matter of the presentinvention unclear, the detailed of the known art or functions may beskipped. Hereinafter, some embodiments of the present disclosure will bedescribed in detail with reference to the accompanying illustrativedrawings. In the drawings, like reference numerals are used to denotelike elements throughout the drawings, even if they are shown ondifferent drawings. Further, in the following description of the presentdisclosure, a detailed description of known functions and configurationsincorporated herein will be omitted when it may make the subject matterof the present disclosure rather unclear.

In addition, terms, such as first, second, A, B, (A), (B) or the likemay be used herein when describing components of the present disclosure.Each of these terminologies is not used to define an essence, order orsequence of a corresponding component but used merely to distinguish thecorresponding component from other component(s). In describing thepositional relationship between components, if two or more componentsare described as being “connected”, “combined”, or “coupled” to eachother, it should be understood that two or more components may bedirectly “connected”, “combined”, or “coupled” to each other, and thattwo or more components may be “connected”, “combined”, or “coupled” toeach other with another component “interposed” therebetween. In thiscase, another component may be included in at least one of the two ormore components that are “connected”, “combined”, or “coupled” to eachother.

The terms or technical denotations used herein are provided solely forthe purpose of describing specific embodiments and the technical spiritis not limited thereto. The terms used herein may be interpreted asgenerally appreciated by one of ordinary skill in the art unless definedotherwise. As used herein, terms wrong or inappropriate for representingthe spirit of the present invention may be replaced with and understoodas more proper ones to represent the spirit of the present invention byone of ordinary skill in the art. General terms as used herein should beinterpreted in the context of the specification or as defined indictionaries.

The wireless communication system in the present specification refers toa system for providing various communication services, such as a voiceservice and a data service, using radio resources. The wirelesscommunication system may include a user equipment (UE), a base station,a core network, and the like.

Embodiments disclosed below may be applied to a wireless communicationsystem using various radio access technologies. For example, theembodiments may be applied to various radio access technologies such ascode division multiple access (CDMA), frequency division multiple access(FDMA), time division multiple access (TDMA), orthogonal frequencydivision multiple access (OFDMA), single-carrier frequency divisionmultiple access (SC-FDMA), non-orthogonal multiple access (NOMA), or thelike. In addition, the radio access technology may refer to respectivegeneration communication technologies established by variouscommunication organizations, such as 3GPP, 3GPP2, Wi-Fi, Bluetooth,IEEE, ITU, or the like, as well as a specific access technology. Forexample, CDMA may be implemented as a wireless technology such asuniversal terrestrial radio access (UTRA) or CDMA2000. TDMA may beimplemented as a wireless technology such as global system for mobilecommunications (GSM)/general packet radio service (GPRS)/enhanced datarates for GSM evolution (EDGE). OFDMA may be implemented as a wirelesstechnology such as IEEE (Institute of Electrical and ElectronicsEngineers) 802.11 (Wi-Fi), IEEE 802.16 (WiMAX), IEEE 802-20, evolvedUTRA (E-UTRA), and the like. IEEE 802.16m is evolution of IEEE 802.16e,which provides backward compatibility with systems based on IEEE802.16e. UTRA is a part of a universal mobile telecommunications system(UMTS). 3GPP (3rd-generation partnership project) LTE (long-termevolution) is a part of E-UMTS (evolved UMTS) using evolved-UMTSterrestrial radio access (E-UTRA), which adopts OFDMA in a downlink andSC-FDMA in an uplink. As described above, the embodiments may be appliedto radio access technologies that have been launched or commercialized,and may be applied to radio access technologies that are being developedor will be developed in the future.

The UE used in the specification must be interpreted as a broad meaningthat indicates a device including a wireless communication module thatcommunicates with a base station in a wireless communication system. Forexample, the UE includes user equipment (UE) in WCDMA, LTE, NR, HSPA,IMT-2020 (5G or New Radio), and the like, a mobile station in GSM, auser terminal (UT), a subscriber station (SS), a wireless device, andthe like. In addition, the UE may be a portable user device, such as asmart phone, or may be a vehicle, a device including a wirelesscommunication module in the vehicle, and the like in a V2X communicationsystem according to the usage type thereof. In the case of amachine-type communication (MTC) system, the UE may refer to an MTCterminal, or an M2M terminal, which employs a communication modulecapable of performing machine-type communication.

A base station or a cell in the present specification refers to an endthat communicates with a UE through a network and encompasses variouscoverage regions such as a Node-B, an evolved Node-B (eNB), a gNode-B, alow-power node (LPN), a sector, a site, various types of antennas, abase transceiver system (BTS), an access point, a point (e.g., atransmission point, a reception point, or a transmission/receptionpoint), a relay node, a megacell, a macrocell, a microcell, a picocell,a femtocell, a remote radio head (RRH), a radio unit (RU), a small cell,and the like.

The various cells listed above are provided with a base stationcontrolling one or more cells, and the base station may be interpretedas two meanings. The base station may be 1) a device for providing amegacell, a macrocell, a microcell, a picocell, a femtocell, or a smallcell in connection with a wireless region, or the base station may be 2)a wireless region itself. In the above description 1), the base stationmay be the devices controlled by the same entity and providingpredetermined wireless regions or all devices interacting with eachother and cooperatively configuring a wireless region. For example, thebase station may be a point, a transmission/reception point, atransmission point, a reception point, and the like according to theconfiguration method of the wireless region. In the above description2), the base station may be the wireless region in which a userequipment (UE) may be enabled to transmit data to and receive data fromthe other UE or a neighboring base station.

In this specification, the cell may refer to coverage of a signaltransmitted from a transmission/reception point, a component carrierhaving coverage of a signal transmitted from a transmission/receptionpoint (or a transmission point), or a transmission/reception pointitself.

An uplink (UL) refers to a scheme of transmitting data from a UE to abase station, and a downlink (DL) refers to a scheme of transmittingdata from a base station to a UE. The downlink may mean communication orcommunication paths from multiple transmission/reception points to a UE,and the uplink may mean communication or communication paths from a UEto multiple transmission/reception points. In the downlink, atransmitter may be a part of the multiple transmission/reception points,and a receiver may be a part of the UE. In addition, in the uplink, thetransmitter may be a part of the UE, and the receiver may be a part ofthe multiple transmission/reception points.

The uplink and downlink transmit and receive control information over acontrol channel, such as a physical downlink control channel (PDCCH) anda physical uplink control channel (PUCCH). The uplink and downlinktransmit and receive data over a data channel such as a physicaldownlink shared channel (PDSCH) and a physical uplink shared channel(PUSCH). Hereinafter, the transmission and reception of a signal over achannel, such as PUCCH, PUSCH, PDCCH, PDSCH, or the like, may beexpressed as “PUCCH, PUSCH, PDCCH, PDSCH, or the like is transmitted andreceived”.

For the sake of clarity, the following description will focus on 3GPPLTE/LTE-A/NR (New Radio) communication systems, but technical featuresof the disclosure are not limited to the corresponding communicationsystems.

The 3GPP has been developing a 5G (5th-Generation) communicationtechnology in order to meet the requirements of a next-generation radioaccess technology of ITU-R after studying 4G (4th-generation)communication technology. Specifically, 3GPP is developing, as a 5Gcommunication technology, LTE-A pro by improving the LTE-Advancedtechnology so as to conform to the requirements of ITU-R and a new NRcommunication technology that is totally different from 4G communicationtechnology. LTE-A pro and NR all refer to the 5G communicationtechnology. Hereinafter, the 5G communication technology will bedescribed on the basis of NR unless a specific communication technologyis specified.

Various operating scenarios have been defined in NR in consideration ofsatellites, automobiles, new verticals, and the like in the typical 4GLTE scenarios so as to support an enhanced mobile broadband (eMBB)scenario in terms of services, a massive machine-type communication(mMTC) scenario in which UEs spread over a broad region at a high UEdensity, thereby requiring low data rates and asynchronous connections,and an ultra-reliability and low-latency (URLLC) scenario that requireshigh responsiveness and reliability and supports high-speed mobility.

In order to satisfy such scenarios, NR introduces a wirelesscommunication system employing a new waveform and frame structuretechnology, a low-latency technology, a super-high frequency band(mmWave) support technology, and a forward compatible provisiontechnology. In particular, the NR system has various technologicalchanges in terms of flexibility in order to provide forwardcompatibility. The primary technical features of NR will be describedbelow with reference to the drawings.

<Overview of NR System>

FIG. 1 is a view schematically illustrating an NR system to which thepresent embodiment is applicable.

Referring to FIG. 1, the NR system is divided into a 5G core network(5GC) and an NG-RAN part. The NG-RAN includes gNBs and ng-eNBs providinguser plane (SDAP/PDCP/RLC/MAC/PHY) and user equipment (UE) control plane(RRC) protocol ends. The gNBs or the gNB and the ng-eNB are connected toeach other through Xn interfaces. The gNB and the ng-eNB are connectedto the 5GC through NG interfaces, respectively. The 5GC may beconfigured to include an access and mobility management function (AMF)for managing a control plane, such as a UE connection and mobilitycontrol function, and a user plane function (UPF) controlling user data.NR supports both frequency bands below 6 GHz (frequency range 1 FR1 FR1)and frequency bands equal to or greater than 6 GHz (frequency range 2FR2 FR2).

The gNB denotes a base station that provides a UE with an NR user planeand control plane protocol end. The ng-eNB denotes a base station thatprovides a UE with an E-UTRA user plane and control plane protocol end.The base station described in the present specification should beunderstood as encompassing the gNB and the ng-eNB. However, the basestation may be also used to refer to the gNB or the ng-eNB separatelyfrom each other, as necessary.

<NR Waveform, Numerology, and Frame Structure>

NR uses a CP-OFDM waveform using a cyclic prefix for downlinktransmission and uses CP-OFDM or DFT-s-OFDM for uplink transmission.OFDM technology is easy to combine with a multiple-input multiple-output(MIMO) scheme and allows a low-complexity receiver to be used with highfrequency efficiency.

Since the three scenarios described above have different requirementsfor data rates, delay rates, coverage, and the like from each other inNR, it is necessary to efficiently satisfy the requirements for eachscenario over frequency bands constituting the NR system. To this end, atechnique for efficiently multiplexing radio resources based on aplurality of different numerologies has been proposed.

Specifically, the NR transmission numerology is determined on the basisof subcarrier spacing and a cyclic prefix (CP). As shown in Table 1below, “μ” is used as an exponential value of 2 so as to be changedexponentially on the basis of 15 kHz.

TABLE 1 Subcarrier Cyclic Supported for Supported for μ spacing prefixdata synch 0 15 Normal Yes Yes 1 30 Normal Yes Yes 2 60 Normal, Yes NoExtended 3 120 Normal Yes Yes 4 240 Normal No Yes

As shown in Table 1 above, NR may have five types of numerologiesaccording to subcarrier spacing. This is different from LTE, which isone of the 4G-communication technologies, in which the subcarrierspacing is fixed to 15 kHz. Specifically, in NR, subcarrier spacing usedfor data transmission is 15, 30, 60, or 120 kHz, and subcarrier spacingused for synchronization signal transmission is 15, 30, 120, or 240 kHz.In addition, an extended CP is applied only to the subcarrier spacing of60 kHz. A frame that includes 10 subframes each having the same lengthof 1 ms and has a length of 10 ms is defined in the frame structure inNR. One frame may be divided into half frames of 5 ms, and each halfframe includes 5 subframes. In the case of a subcarrier spacing of 15kHz, one subframe includes one slot, and each slot includes 14 OFDMsymbols. FIG. 2 is a view for explaining a frame structure in an NRsystem to which the present embodiment may be applied. Referring to FIG.2, a slot includes 14 OFDM symbols, which are fixed, in the case of anormal CP, but the length of the slot in the time domain may be varieddepending on subcarrier spacing. For example, in the case of anumerology having a subcarrier spacing of 15 kHz, the slot is configuredto have the same length of 1 ms as that of the subframe. On the otherhand, in the case of a numerology having a subcarrier spacing of 30 kHz,the slot includes 14 OFDM symbols, but one subframe may include twoslots each having a length of 0.5 ms. That is, the subframe and theframe may be defined using a fixed time length, and the slot may bedefined as the number of symbols such that the time length thereof isvaried depending on the subcarrier spacing.

NR defines a basic unit of scheduling as a slot and also introduces aminislot (or a subslot or a non-slot-based schedule) in order to reducea transmission delay of a radio section. If wide subcarrier spacing isused, the length of one slot is shortened in inverse proportion thereto,thereby reducing a transmission delay in the radio section. A minislot(or subslot) is intended to efficiently support URLLC scenarios, and theminislot may be scheduled in 2, 4, or 7 symbol units.

In addition, unlike LTE, NR defines uplink and downlink resourceallocation as a symbol level in one slot. In order to reduce a HARQdelay, the slot structure capable of directly transmitting HARQ ACK/NACKin a transmission slot has been defined. Such a slot structure isreferred to as a “self-contained structure”, which will be described.

NR was designed to support a total of 256 slot formats, and 62 slotformats thereof are used in 3GPP Rel-15. In addition, NR supports acommon frame structure constituting an FDD or TDD frame throughcombinations of various slots. For example, NR supports i) a slotstructure in which all symbols of a slot are configured for a downlink,ii) a slot structure in which all symbols are configured for an uplink,and iii) a slot structure in which downlink symbols and uplink symbolsare mixed. In addition, NR supports data transmission that is scheduledto be distributed to one or more slots. Accordingly, the base stationmay inform the UE of whether the slot is a downlink slot, an uplinkslot, or a flexible slot using a slot format indicator (SFI). The basestation may inform a slot format by instructing, using the SFI, theindex of a table configured through UE-specific radio resource control(RRC) signaling. Further, the base station may dynamically instruct theslot format through downlink control information (DCI) or may staticallyor quasi-statically instruct the same through RRC signaling.

<Physical Resources of NR>

With regard to physical resources in NR, antenna ports, resource grids,resource elements, resource blocks, bandwidth parts, and the like aretaken into consideration.

The antenna port is defined to infer a channel carrying a symbol on anantenna port from the other channel carrying another symbol on the sameantenna port. If large-scale properties of a channel carrying a symbolon an antenna port can be inferred from the other channel carrying asymbol on another antenna port, the two antenna ports may have aquasi-co-located or quasi-co-location (QC/QCL) relationship. Thelarge-scale properties include at least one of delay spread, Dopplerspread, a frequency shift, an average received power, and a receivedtiming.

FIG. 3 illustrates resource grids supported by a radio access technologyin accordance with embodiments of the present disclosure.

Referring to FIG. 3, resource grids may exist according to respectivenumerologies because NR supports a plurality of numerologies in the samecarrier. In addition, the resource grids may exist depending on antennaports, subcarrier spacing, and transmission directions.

A resource block includes 12 subcarriers and is defined only in thefrequency domain. In addition, a resource element includes one OFDMsymbol and one subcarrier. Therefore, as shown in FIG. 3, the size ofone resource block may be varied according to the subcarrier spacing.Further, “Point A” that acts as a common reference point for theresource block grids, a common resource block, and a virtual resourceblock are defined in NR.

FIG. 4 illustrates bandwidth parts supported by a radio accesstechnology in accordance with embodiments of the present disclosure.

Unlike LTE in which the carrier bandwidth is fixed to 20 MHz, themaximum carrier bandwidth is configured as 50 MHz to 400 MHz dependingon the subcarrier spacing in NR. Therefore, it is not assumed that allUEs use the entire carrier bandwidth. Accordingly, as shown in FIG. 4,bandwidth parts (BWPs) may be specified within the carrier bandwidth inNR so that the UE may use the same. In addition, the bandwidth part maybe associated with one numerology, may include a subset of consecutivecommon resource blocks, and may be activated dynamically over time. TheUE has up to four bandwidth parts in each of the uplink and thedownlink. The UE transmits and receives data using an activatedbandwidth part during a given time.

In the case of a paired spectrum, uplink and downlink bandwidth partsare configured independently. In the case of an unpaired spectrum, inorder to prevent unnecessary frequency re-tuning between a downlinkoperation and an uplink operation, the downlink bandwidth part and theuplink bandwidth part are configured in pairs to share a centerfrequency.

<Initial Access in NR>

In NR, a UE performs a cell search and a random access procedure inorder to access and communicates with a base station.

The cell search is a procedure of the UE for synchronizing with a cellof a corresponding base station using a synchronization signal block(SSB) transmitted from the base station and acquiring a physical-layercell ID and system information.

FIG. 5 illustrates an example of a synchronization signal block in aradio access technology in accordance with embodiments of the presentdisclosure.

Referring to FIG. 5, the SSB includes a primary synchronization signal(PSS) and a secondary synchronization signal (SSS), which occupy onesymbol and 127 subcarriers, and PBCHs spanning three OFDM symbols and240 subcarriers.

The UE monitors the SSB in the time and frequency domain, therebyreceiving the SSB.

The SSB may be transmitted up to 64 times for 5 ms. A plurality of SSBsare transmitted by different transmission beams within a time of 5 ms,and the UE performs detection on the assumption that the SSB istransmitted every 20 ms based on a specific beam used for transmission.The number of beams that may be used for SSB transmission within 5 msmay be increased as the frequency band is increased. For example, up to4 SSB beams may be transmitted at a frequency band of 3 GHz or less, andup to 8 SSB beams may be transmitted at a frequency band of 3 to 6 GHz.In addition, the SSBs may be transmitted using up to 64 different beamsat a frequency band of 6 GHz or more.

One slot includes two SSBs, and a start symbol and the number ofrepetitions in the slot are determined according to subcarrier spacingas follows.

Unlike the SS in the typical LTE system, the SSB is not transmitted atthe center frequency of a carrier bandwidth. That is, the SSB may alsobe transmitted at the frequency other than the center of the systemband, and a plurality of SSBs may be transmitted in the frequency domainin the case of supporting a broadband operation. Accordingly, the UEmonitors the SSB using a synchronization raster, which is a candidatefrequency position for monitoring the SSB. A carrier raster and asynchronization raster, which are the center frequency positioninformation of the channel for the initial connection, were newlydefined in NR, and the synchronization raster may support a fast SSBsearch of the UE because the frequency spacing thereof is configured tobe wider than that of the carrier raster.

The UE may acquire an MIB over the PBCH of the SSB. The MIB (masterinformation block) includes minimum information for the UE to receiveremaining minimum system information (RMSI) broadcast by the network. Inaddition, the PBCH may include information on the position of the firstDM-RS symbol in the time domain, information for the UE to monitor SIB1(e.g., SIB1 numerology information, information related to SIB1 CORESET,search space information, PDCCH-related parameter information, etc.),offset information between the common resource block and the SSB (theposition of an absolute SSB in the carrier is transmitted via SIB1), andthe like. The SIB1 numerology information is also applied to message 2or message 4 used in the random access procedure for the UE to accessthe base station after completing the cell search procedure.

The above-mentioned RMSI may mean SIB1 (system information block 1), andSIB1 is broadcast periodically (e.g., 160 ms) in the cell. SIB1 includesinformation necessary for the UE to perform the initial random accessprocedure, and SIB1 is periodically transmitted over a PDSCH. In orderto receive SIB1, the UE must receive numerology information used for theSIB1 transmission and the CORESET (control resource set) informationused for scheduling of SIB1 over a PBCH. The UE identifies schedulinginformation for SIB1 using SI-RNTI in the CORESET. The UE acquires SIB1on the PDSCH according to scheduling information. The remaining SIBsother than SIB1 may be periodically transmitted, or the remaining SIBsmay be transmitted according to the request of the UE.

FIG. 6 is a view for explaining a random access procedure in a radioaccess technology to which the present embodiment is applicable.

Referring to FIG. 6, if a cell search is completed, the UE transmits arandom access preamble for random access to the base station. The randomaccess preamble is transmitted over a PRACH. Specifically, the randomaccess preamble is periodically transmitted to the base station over thePRACH that includes consecutive radio resources in a specific slotrepeated. In general, a contention-based random access procedure isperformed when the UE makes initial access to a cell, and anon-contention-based random access procedure is performed when the UEperforms random access for beam failure recovery (BFR).

The UE receives a random access response to the transmitted randomaccess preamble. The random access response may include a random accesspreamble identifier (ID), UL Grant (uplink radio resource), a temporaryC-RNTI (temporary cell-radio network temporary identifier), and a TAC(time alignment command). Since one random access response may includerandom access response information for one or more UEs, the randomaccess preamble identifier may be included in order to indicate the UEfor which the included UL Grant, temporary C-RNTI, and TAC are valid.The random access preamble identifier may be an identifier of the randomaccess preamble received by the base station. The TAC may be included asinformation for the UE to adjust uplink synchronization. The randomaccess response may be indicated by a random access identifier on thePDCCH, i.e., a random access-radio network temporary identifier(RA-RNTI).

Upon receiving a valid random access response, the UE processesinformation included in the random access response and performsscheduled transmission to the base station. For example, the UE appliesthe TAC and stores the temporary C-RNTI. In addition, the UE transmits,to the base station, data stored in the buffer of the UE or newlygenerated data using the UL Grant. In this case, information foridentifying the UE must be included in the data.

Lastly, the UE receives a downlink message to resolve the contention.

As used herein, the frequency, frame, subframe, resource, resourceblock, region, band, subband, control channel, data channel,synchronization signal, various reference signals, various signals, andvarious messages related to new radio (NR) may be interpreted in variousmeanings as currently used or to be used in the future.

LTE Relay Technology

In LTE technology, relay technology has been used for expanding cellcoverage via use of additional network nodes, called relay nodes (RNs).The LTE RN performs relaying for user plane data and control plane dataat the IP packet level. Further, services are provided via only one RNbetween the UE and the donor base station (donor eNB, DeNB) which is thebase station serving the relay node. That is, single-hop relaying onlyis supported between the UE and the DeNB.

FIG. 7 is a view illustrating an exemplary relay-based user planeprotocol structure in LTE technology.

Referring to FIG. 7, a UE 700 communicates with a donor base station 720via a relay node 710. The donor base station 720 transfers data from theUE 700 to a gateway 730. The UE 700 is composed of an L1 physical layer,an L2 layer, an IP layer, a TCP/UDP layer, and an App. layer. The relaynode 710 is connected with the UE 700 via the L1 and L2 layers and isconnected with the donor base station 720 via a GTP-u layer over the IPlayer, transmitting and receiving data. To that end, the relay protocolin LTE technology is configured as shown in FIG. 7.

FIG. 8 is a view illustrating a relay node (RN) startup procedure in LTEtechnology.

An RN startup procedure of FIGS. 8A and 8B is for starting the RNoperation in LTE relay technology. The RN startup procedure is performedto configure parameters necessary for the RN.

Referring to FIGS. 8A and 8B, after an RN 800 is powered on (S805), theRN 800 performs a two-phase startup procedure. When the RN 800 powerson, two phases are provided because it is not known what cell the RN 800is allowed to network-register (attach). Since all base stations are notsupported to serve the RN 800, the RN 800 needs to identify what cellsupports the operation of the RN 800. If the RN 800 is already aware ofthe attachable cells, phase I may be skipped and phase II may beimmediately performed.

Referring to FIG. 8A, phase I is described below.

Phase I Attach for RN preconfiguration.

Upon power-up, the RN 800 (e.g., UE) attaches to the E-UTRAN/EPC (S815)and searches for initial configuration parameters including a list ofDeNB cells from an RN OAM 850 (S825). After operation S825 is completed,the RN 800 is detached from the network (S835) and triggers phase IIdescribed below. The MME 820, as a normal UE, performs selection on anS_GW and a P-GW 830 for the RN 800. (The RN attaches to the E-UTRAN/EPCas a UE at power-up and retrieves initial configuration parameters,including the list of DeNB cells, from RN OAM. After this operation iscomplete, the RN detaches from the network as a UE and triggers PhaseII. The MME performs the S-GW and P-GW selection for the RN as a normalUE.)

Referring to FIG. 8B, phase II is described below.

Phase II Attach for RN operation.

Referring to FIG. 8B, the RN 800 performs connection to a DeNB 810selected from the list gathered in phase I to start relay operations(S806).

If the DeNB 810 starts a bearer configuration for S1/X2, the RN 800starts an S1 and X2 connection configuration with the DeNB 810. Further,the DeNB 810 initiates an RN reconfiguration procedure via RRC signalingon an RN-specific parameter (S807). (The RN connects to a DeNB selectedfrom the list acquired during Phase I to start relay operations. Afterthe DeNB initiates setup of bearer for S1/X2, the RN initiates the setupof S1 and X2 associations with the DeNB. In addition, the DeNB mayinitiate an RN reconfiguration procedure via RRC signaling forRN-specific parameters.)

After performing an S1 setup with the RN 800 (S808), the DeNB 810performs an S1 eNB configuration update procedure when the configurationdata is updated by RN connection (S809). Further, after performing an X2setup with the RN 800 (S811), the DeNB 810 performs an X2 eNBconfiguration update procedure and updates cell information (S812).(After the S1 setup, the DeNB performs the S eNB Configuration Updateprocedure(s), if the configuration data for the DeNB is updated due tothe RN attach. After the X2 setup, the DeNB performs the X2 eNBConfiguration Update procedure(s) to update the cell information). InPhase II, the ECGIs of the RN cell are configured by RN OAM (In thisphase the RN cells' ECGIs are configured by RN OAM).

If phase II is completed, the RN 800, as a relay, starts its operation(S813).

As such, in the typical LTE relay technology, the RN supports onlysingle-hop relaying, and most of the relay configuration is provided viastatic OAM. From the UE's point of view, the RN plays a role as a basestation, and the RN recognizes the donor base station as a core networkentity and configures a UE context in the RN. Thus, most of the RNconfiguration is made by being instructed via OAM and, in the entire RNdevice, only a specific radio configuration (e.g., RN subframeconfiguration) is instructed by the determination of the donor basestation 720 and is configured. Thus, if multiple hops are supportedbetween the UE and the base station (donor base station), it isdifficult to efficiently configure according to the service requirementsper UE. Upon attempting to support multiple hop relays via the typicalLTE technology, it is impossible to separately process data via aplurality of relay nodes. Further, over-IP layer signaling and dataprocessing may increase latency.

High Layer Functional Split

The next-generation radio access network (hereinafter, referred to asNR, 5G, or NG-RAN for ease of description) may be provides separatelyinto concentrated nodes (hereinafter, denoted central units (CUs) forease of description) and distributed nodes (hereinafter, denoteddistributed units (DUs) for ease of description) to support efficientnetwork buildups. That is, a base station may be separated into a CU anda DU from a logical or physical point of view. The base station as usedherein refers to a base station adopting NR technology and, to bedistinguished from LTE base station (eNB), may be denoted a gNB.Further, unless stated otherwise, NR technology may be applied to basestations, donor base stations, and relay nodes.

The CU is a logical node hosting RRC, SDAP, and PDCP protocol. Or, theCU means a logical node hosting RRC and higher layer L2 protocol (PDCP).The CU controls the operation of one or more DUs. The CU terminates theF1 interface connected with DU. (gNB Central Unit (gNB-CU), a logicalnode hosting RRC, SDAP and PDCP protocols, and controls the operation ofone or more gNB-DUs. The gNB-CU also terminates F1 interface connectedwith the gNB-DU.)

The DU is a logical node hosting RLC, MAC, and PHY layer. The operationof DU is partially controlled by the CU. One DU supports one or morecells. One cell is supported by only one DU. The DU terminates the F1interface connected with CU. (gNB Distributed Unit (gNB-DU), a logicalnode hosting RLC, MAC and PHY layers, and its operation is partlycontrolled by gNB-CU. One gNB-DU supports one or multiple cells. Onecell is supported by only one gNB-DU. The gNB-DU terminates F1 interfaceconnected with the gNB-CU.)

The NG-RAN consists of a set of gNBs connected to the 5GC through theNG.

The gNBs can be interconnected through the Xn. A gNB may include agNB-CU and gNB-DUs. A gNB-CU and a gNB-DU is connected via F1 logicalinterface. One gNB-DU is connected to only one gNB-CU. For NG-RAN, theNG and Xn-C interfaces for a gNB consisting of a gNB-CU and gNB-DUs,terminate in the gNB-CU.

As such, the F1 interface is an interface for providing mutual accessbetween CU and DU and uses an F1AP (The F1 Application Protocol) toprovide a signaling procedure on the corresponding interface.

For EN-DC, the S1-U and X2-C interfaces for a gNB including a gNB-CU andgNB-DUs, terminate in the gNB-CU. The gNB-CU and connected gNB-DUs areonly visible to other gNBs and the 5GC as a gNB.

New Radio (NR)-Based Relay

The 3GPP has been conducting initial standardization for 5G radiocommunication technology (NR) to meet various requirements fromtechnology development. NR which is able to use high-frequency bandsuses a wider bandwidth and multi-beam system as compared with LTE andmay have more utility for relay technology. Thus, the operator may moreeasily build up a dense network of self-backhauled NR cells. However,the mmWave band may have the drawback of being likely to experiencesevere short-term blocking. Small coverage and beam operation of themmWave band may need connection to the base station connectedwiredly/via optical fiber through a multi-hop relay. In this case, thetypical LTE-based relay technology cannot connect the UE to the basestation connected wiredly/via optical fiber. In particular, themulti-hop relay needs to process data in multiple hops and may thus bedifficult to use upon 5G service transmission which is sensitive todelay. Thus, research is required for various protocol structures tomeet the quality for each service in multiple hops, but no detailedtechnology therefor has been yet proposed.

The present disclosure introduces an NR relay structure capable ofconfiguring a plurality of hop relays to thereby separately process datafor the requirements per UE or per service in an effective manner. Alsothe present disclosure introduces a specific procedure and device forconnecting the UE to the base station via multi-hop relay nodes in an NRrelay structure.

Embodiments described below may be practiced individually or incombination. For ease of description, the description focuses primarilyon the case where NR access to the NR UE is relayed to the NR basestation (donor base station) via NR-based radio self-backhauling.However, this is merely an example for description, and each embodimentdescribed below may also be applied where LTE access to the LTE UE isrelayed to the LTE base station (donor base station) via NR-based radioself-backhauling.

In the disclosure, a donor base station denotes a radio network node (orbase station, gNB, or part of gNB) that terminates the interface (NGinterface, e.g., N2, or N3 interface) for the core network. The donorbase station may be physically connected to the core network or otherbase stations wiredly/via optical fiber. Further, the donor base stationmay configure a backhaul with other NR nodes, e.g., base stations, CUs,DUs, and core network nodes (e.g., AMF or UPF), using NR radiotechnology. The donor base station may include one CU and one or moreDUs, as does the NR base station. The term “donor base station” may bereplaced with other terms, such as IAB-DN, DgNB, DN, or Donor basestation.

Meanwhile, an integrated access and backhaul (IAB) node means a nodethat supports access to UE and radio self-backhauling using NR radiotechnology. The IAB node may configure a backhaul to other NR node usingNR radio technology. Further, the IAB node may physically not connect toother NR node wiredly/via optical fiber. The term “IAB node” may bereplaced with other terms, such as NR-RN, NR relay, or integrated node.In the following description, it is termed a relay node or IAB node.

The Un interface refers to an interface between IAB nodes or between theIAB node and the donor base station. The term “Un interface” may bereplaced with other terms, such as IAB backhaul interface, U-IABinterface, or Ui interface.

When the UE accesses the donor base station via the multi-hop IAB node,the IAB nodes should be able to effectively separate, process andtransfer user data traffic between the UE and the donor base station. Asan example, the IAB node should be able to determine a next hop andtransfer corresponding uplink data to the next hop to be able toseparately transfer the uplink data belonging to a specific radiobearer, received from a specific UE, to the donor base station. Asanother example, the IAB node should be able to determine a next hop andtransfer corresponding downlink data to the next hop to be able toseparately process/transfer the downlink data belonging to a specificradio bearer of a specific UE, received from a specific donor basestation, to the UE.

To implement such operations, the multi-hop IAB node and the donor basestation should perform RRC connection configuration. That is, similar tothe RN startup procedure described above in connection with FIG. 8, theIAB node may perform a procedure for configuring parameters necessaryfor the IAB node to start IAB node operations.

FIG. 9 is a view illustrating an RRC connection configuration procedureusing a relay node according to an embodiment.

The procedure described in connection with FIG. 9 may be applied tovarious protocol structures described below. In connection with FIG. 9,the description focuses primarily on the case where the UE and the donorbase station transmit and receive data via two hops (e.g., IAB 1 and IAB2) for ease of description. This is merely for ease of description, andthe same may also be applied where any number of IAB nodes are included.

Referring to FIG. 9, the donor base station 903 performs a connectionsetup operation with the IAB node (IAB 2) 902 directly connected via theradio interface (S910). If the connection setup operation is completed,the donor base station 903 performs a connection setup operation withanother IAB node (IAB 1) 901 (S915).

The UE 900 transmits a random access preamble to the IAB 1 node 901,initiating a random access operation to the IAB 1 node 901 (S920). TheIAB 1 node 901 includes a response to the random access preamble in arandom access response message and transmits the same to the UE 900(S925). The UE 900 transmits an RRC connection request message,initiating an RRC connection configuration procedure with the donor basestation 903 (S930). The donor base station 903 configures a signalingradio bearer for transmission of a control message of the UE 900 or theIAB 1 node 901 or the IAB 2 node 902 on the backhaul interface betweenthe IAB 2 node 902 and the donor base station 903 via an RRC connectionreconfiguration procedure with the IAB 2 node 902 (S935). Further, thedonor base station 903 configures a signaling radio bearer fortransmission of a control message of the UE 900 or the IAB 1 node 901 onthe interface between the IAB 1 node 901 and the donor base station 903via an RRC connection reconfiguration procedure with the IAB 1 node 901(S935).

The donor base station 903 sets up an RRC connection to the UE 900 bytransmitting an RRC connection setup message to the UE 900 (S945). TheUE 900 sets up an RRC connection with the donor base station 903 usingthe received RRC connection setup message and transmits an RRCconnection setup complete message to the donor base station 903 via theIAB 1 node 901 and/or the IAB 2 node 902 (S950).

If the RRC connection setup with the UE 900 is completed, the donor basestation 903 performs signaling with a core network entity (S955).Accordingly, it receives PDU session ID, S-NSSAI, QFI (QoS flowIndicator), QFI-associated QoS profile information to be configured inthe UE 900 from the core network entity. Thereafter, the donor basestation 903 performs a radio resource configuration procedure forseparately relaying data radio bearers for the IAB 1 node 901, the IAB 2node 902, and the UE 900 (S965 and S970). The donor base station 903transmits an RRC connection reconfiguration message, configuring a radioresource in the UE 900 (S970). The UE 900 transmits an RRC connectionreconfiguration complete message, providing an acknowledgement for radioresource configuration (S975).

As described above, the UE and the donor base station configure an RRCconnection and radio resources (radio bearers) via the relay node (IABnode).

Each step of FIG. 9 is described below stepwise and in greater detail.

Connection Setup of the IAB Node (IAB 2) Directly Connected with theDonor Base Station Via the Radio Interface

If the IAB node is directly connected with the donor base station viathe radio interface, the IAB node may configure an RRC connection to thedonor base station and perform network registration. For example, if theIAB node selects the cell provided by the donor base station and isconnected to the donor base station via the cell, the IAB node mayconfigure an RRC connection to the donor base station and performnetwork registration. The IAB node may extract initial configurationparameters including the donor base station cell list from the (IAB) OAMfor preconfiguration of the IAB node. Thereafter, for IAB operation, theIAB node may select the cell with the best radio quality from among thecells included in the donor base station cell list, configure an RRCconnection via the cell, and perform an IAB node operation.

As an example, the IAB node and the cells of the IAB node may beconfigured by IAB OAM. The IAB node and IAB node cell configuration maybe performed together with extracting the initial configurationparameters including the donor base station cell list or may beperformed in phase II during which it, as an IAB node, performs networkregistration. Alternatively, it may be preconfigured in the IAB node.

As an example, the radio resource configuration for the IAB node and IABnode cells may be made by being instructed by the donor base station.The radio resource configuration operation may be performed in phase Iduring which the IAB node, as a UE, performs network registration. Or,the radio resource configuration operation may be performed in phase IIduring which it, as an IAB node, performs network registration. Or, theradio resource configuration operation may be performed andconfiguration when triggered by the donor base station. If the NR-basedIAB node supports multi-hop topology, the donor base station may controlthe radio resources of the IAB node for efficient radio resourcecontrol. By so doing, when the UE accesses the donor base station andtransmits/receives data, the IAB nodes may effectively separate andprocess/transfer user data traffic between the UE and the donor basestation according to the QoS parameters.

As another example, the IAB node transmits a request message for settingup an interface between the IAB node and the donor base station to thedonor base station. For ease of description, an F3 interface denotes theinterface between the IAB node and the donor base station. However, thepresent embodiments are not limited thereto. For example, the F3interface may be replaced with another term. The F3 interface may denotethe interface between the donor base station and the access IAB node(e.g., first hop IAB node) serving the UE. Where the donor base stationis split into CU and DU, the F3 interface may indicate the interfacebetween the donor base station DU and the access IAB node serving the UEor the interface between the donor base station CU and the access IABnode serving the UE.

Similar to the F1 application protocol (F1AP) of the F1 interface whichis the interface between CU and DU, there may be provided a higher layerprotocol to provide a signaling procedure between the IAB node and thedonor base station on the F3 interface. For ease of description, such ahigher layer protocol is referred to as an F3 application protocol(F3AP). For example, the above-described setup request message for theinterface between the IAB node and the donor base station denotes anF3AP message used to exchange data of the application level necessaryfor the IAB node and donor base station to correctly operate on the F3interface.

The F3 interface setup request message includes a cell list configuredin the IAB node. Or, the F3 interface setup request message may includea cell list configured in the IAB node and having been ready to beactivated or a candidate cell list that may be configured/activated. TheF3 interface setup request message may be included and transmitted in anuplink RRC message. As an example, the uplink RRC message may be an RRCsetup complete message, a UL information transfer message, or a UEassistant information message.

The donor base station may ensure connectivity to the core network. Forsuch a reason, the donor base station may perform an NG setup or gNBconfiguration update procedure with the 5G core network (5GC).

The donor base station transmits an F3 interface setup response messagebetween the IAB node and the donor base station to the IAB node. The F3interface setup response message may include a cell list to beconfigured in the IAB node. Or, the F3 interface setup response messagemay include a cell list to be activated of the cell list to be activatedin the IAB node or a candidate cell list. The F3 interface setupresponse message may be included and transmitted in a downlink RRCmessage. As an example, the downlink RRC message may be an RRCconnection reconfiguration message or DL information transfer message.If the IAB node succeeds in activating the cell, the activated cell isoperated.

2) Connection Setup of the IAB Node (IAB 1) Connected Via the RadioInterface Provided by Another IAB Node (e.g., IAB 2)

If the IAB node connects to the donor base station via another IAB node,the IAB node may configure an RRC connection to the donor base stationvia the other IAB node and perform network registration. For example, ifthe IAB node selects a cell (e.g., activated cell) provided by the otherIAB node and connects to the donor base station via another IAB node,the IAB node may configure an RRC connection to the donor base stationvia the other IAB node and perform network registration.

As an example, for preconfiguration of the IAB node connected to thedonor base station via the other IAB node, the IAB node may extractinitial configuration parameters including the cell list of the otherIAB node than the donor base station cell list from the IAB OAM. Or, theIAB node may extract the initial configuration parameters including thecell list of the other IAB node except for the donor base station celllist from the IAB OAM. Alternatively, the IAB node may extract theinitial configuration parameters including at least one of a donor basestation cell list, a cell list of the other IAB node, an activated celllist of the other IAB node, a cell list of an adjacent IAB node, anactivated cell list of the adjacent IAB node, a cell list of a neighborIAB node, a neighbor cell list, and an neighbor cell list associatedwith the IAB node, from the IAB OAM.

Thereafter, for IAB operation, the IAB node may select the cell with thebest radio quality from among the cells included in the received celllist, configure an RRC connection via the cell, and perform an IAB nodeoperation.

As another example, the donor base station may indicate/configurepreconfiguration information or configuration information for the IABnode connected to the donor base station, to the IAB node through an RRCmessage, via the other IAB node. For example, the preconfigurationinformation or configuration information may include at least oneinformation of a donor base station cell list, a cell list of the otherIAB node, an activated cell list of the other IAB node, a cell list ofan adjacent IAB node, an activated cell list of the adjacent IAB node, acell list of a neighbor IAB node, a neighbor cell list, and an neighborcell list associated with the IAB node. The above-described RRC messagemay be included in an RRC connection release message or RRC connectionreconfiguration message. The donor base station may release the RRCconnection of the IAB node. Thereafter, for IAB operation, the IAB node(or UE) may select the cell with the best radio quality from among thecells included in the received cell list, configure an RRC connectionvia the cell, and perform an IAB node operation.

If the IAB node performs the same cell selection/reselection operationas a normal UE in the idle mode, it would have a high chance that thecell with the best radio quality may be selected/reselected, or the cellwith the best radio quality on the priority frequency may beselected/reselected. However, to efficiently perform a relayingoperation, it may be preferable to consider whether theselected/reselected cell is a cell the donor base station provides orthe number of hops to the donor base station.

To that end, as an example, in selecting/reselecting a cell included inthe received cell list, the IAB node may select/reselect a cellconsidering whether each cell is provided by the donor base station orthe number of hops to the donor base station. Specifically, uponperforming the operation for cell selection/reselection, the IAB nodemay consider (adding or subtracting), as a cell selection criterion (orcell reselection criterion/cell ranking criterion), including one ormore of information for indicating whether the corresponding cell is acell provided by the donor base station or the adjustmentparameter/offset/scaling value according to the number of hops to thedonor base station. The parameters additionally applied to theabove-described cell selection criteria may be applied to one of thefollowing cell selection/cell reselection criterion parameters and beused.

The following equations represent example cell selection criterionvalues.

Srxlev=Q _(rxlevmeas)−(Q _(rxlevmin) +Q_(rxlevminoffset))−Pcompensation−Qoffset_(temp)

Squal=Q _(qualmeas)−(Q _(qualmin) +Q _(qualminoffset))−Qoffset_(temp)

The following table shows values of each parameter in the aboveequations. Further, Qoffset_(temp) means the offset parameter applicableas necessary. In the present disclosure, additional parameters may beapplied to the above equations. In this case, such parameter may beadded or subtracted from the above-described equations.

Srxlev Cell selection RX level value (dB) Squal Cell selection qualityvalue (dB) Q_(rxlevmeas) Measured cell RX revel value (RSRP)Q_(qualmeas) Measured cell quality value (RSRQ) Q_(rxlevmin) Minimumrequired RX level in the cell (dBm) Q_(qualmin,) Minimum requiredquality level in the cell (dB) Q_(rxlevminoffset) OffSet to thesignalled Q_(rxlemin) taken into account in the Srxlev evaluation as aresult of a periodic search for a higher priority PLMN while campednormally in a VPLMN [5] Q_(qualminoffset) OffSet to the signalledQ_(qualmin) taken into account in the Squal evaluation as a result of aperiodic search for a higher priority PLMN while camped normally in aVPLMN [5] Pcompensation max(P_(EMAX) − P_(PowerClass), 0) (dB) P_(EMAX)Maximum TX power level an UE may use when transmitting on the uplink inthe cell (dBm) defined as P_(EMAX) in [TS 36.101] P_(PowerClass) MaximumRF output power of the UE (dBm) according to the UE power class asdefined in [TS 36.101]

Meanwhile, one or more information of the above-described donor basestation cell list, cell list of the other IAB node, parameters (e.g.,information for indicating whether it is a cell provided by the donorbase station, information for indicating the number of hops to the donorbase station, and additional parameters) for IAB node cellselection/cell reselection, and initial configuration parameters of theIAB node may be broadcast via system information for the cell where theIAB node is provided or the cell provided by the donor base station.

Alternatively, one or more information of the above-described donor basestation cell list, cell list of the other IAB node, parameters (e.g.,information for indicating whether it is a cell provided by the donorbase station, information for indicating the number of hops to the donorbase station, and additional parameters) for IAB node cellselection/cell reselection, and initial configuration parameters of theIAB node may be provided via additional system information/on demandsystem information.

Specifically, in NR, the minimum system information which is broadcastat fixed cycles and always receivable by the UE is distinct from othersystem information (RMSI). The minimum system information includes basicinformation necessary for initial access and being broadcast at fixedcycles and may be divided into the master information block transmittedon the BCH and system information block type 1 transmitted on theDL-SCH. In contrast, the other system information RMSI provides theperiod and scheduling information broadcast by the system informationblock type 1. Information for the donor base station provided for theIAB node may not be essential minimum system information. Thus, the UEmay obtain the other system information RMSI in an on-demand mannerbased on the minimum system information. As an example, duringperforming random access, the other system information may be received.As another example, the other system information may be received duringconfiguring RRC connection.

Or, one or more information of the above-described donor base stationcell list, cell list of the other IAB node, parameters (e.g.,information for indicating whether it is a cell provided by the donorbase station, information for indicating the number of hops to the donorbase station, and additional parameters) for IAB node cellselection/cell reselection, and initial configuration parameters of theIAB node may be transmitted to the IAB node via a dedicated RRC messageby the donor base station. For example, the dedicated RRC messagetransmitted by the base station may be an RRC connection release messageor RRC connection reconfiguration message.

Alternatively, one or more information of the above-described donor basestation cell list, cell list of the other IAB node, parameters (e.g.,information for indicating whether it is a cell provided by the donorbase station, information for indicating the number of hops to the donorbase station, and additional parameters) for IAB node cellselection/cell reselection, and initial configuration parameters of theIAB node may be transmitted to the IAB node via an F3AP message by thedonor base station.

Further, the above-described donor base station cell list, cell list ofthe other IAB node, and parameters for cell selection/cell reselectionby the IAB node may be used to perform cell selection/reselection/linkselection for restoring connection to the donor base station by the IABnode when the IAB node experiences a radio link failure (e.g., when theIAB node in connected state detects a failure in radio link to thehigher IAB node). For example, if the IAB node detects a radio linkfailure, the IAB node reconfigures a connection to the donor basestation via another cell. Such procedure may be provided via a normalcell selection procedure and cell selection may be performed among thecells provided via a replacement path preconfigured by the donor basestation. The donor base station may configure information to bereconfigured earlier than others to support quick restoration in the IABnode when any IAB node detects a radio link failure via the RRCdedicated message. The information may include one or more informationof priority cell, priority cell list, priority frequency,reconfiguration candidate cell, reconfiguration candidate cell list,donor base station cell list, cell list of other IAB node, and number ofhops to the donor base station for each cell. Upon detecting a radiolink failure to the donor base station or higher IAB node, the IAB nodereconfigures a connection to the donor base station using theinformation. As an example, the IAB node may perform cell selectionfirst from among the indicated cells. As another example, the IAB nodemay identify the physical cell identifier of each cell via the broadcastsystem information and select the indicated cell. If the radio link ofthe IAB node is reconfigured, the number of hops to the donor basestation of the other IAB node connected to the IAB node is varied. Thedonor base station transfers information for modifying the number ofhops to the donor base station of the cell received by each IAB node oreach IAB node to each IAB node, and the corresponding IAB node receivesthe same, varies the corresponding information, and stores the same. Thecorresponding information may be indicated from the donor base stationto the IAB node via an RRC message or F3AP message.

Meanwhile, the UE may first perform cell selection/cell reselection on acell based on the above-described parameters, such as the informationfor indicating whether the cell is a cell provided by the donor basestation or the information for indicating the number of connection hopsto the donor base station.

3) Random Access Preamble Transmission

Where the UE in idle state selects a cell associated with the IAB 1 nodeaccording to the cell selection/cell reselection criteria, if the UEattempts network access (e.g., the idle UE triggers transmission oftransmit data), the UE initiates a random access procedure to the IAB 1node. The MAC entity of the UE transmits a random access preamble to theIAB 1 node. That is, the UE recognizes the IAB 1 node as a base stationand transmits a random access preamble.

4) Random Access Response

After the UE has transmitted a contention-based random access preamble,the UE starts a random access response window at the beginning of thefirst PDCCH occasion after fixed specific symbol duration from the endof the preamble transmission. While the random access response windowoperates, the UE monitors the PDCCH for the random access responseidentified by the RA-RNTI. Upon receiving the random access responsemessage identified by the RA-RNTI while monitoring PDCCH, the UEperforms the remaining random access procedure using the responsemessage.

5) RRC Connection Request Message Transmission

The UE transmits an RRC connection request message to the IAB 1 node.

The IAB 1 node transmits the RRC connection request message to the donorbase station via the IAB 2 node.

As an example, the IAB 1 node may include the RRC connection requestmessage in an uplink RRC message and transmit the same. As an example,the IAB 1 node may transmit the RRC connection request message via asignaling radio bearer (e.g., a signaling radio bearer configured forSRB0 or SRB1/SRB2 configured for any signaling radio bearer). The RRCconnection request message may be included in an F3AP messagetransmitted to the donor base station via the F3 interface by the IAB 1node and transmitted via the signaling radio bearer. To that end, theF3AP message may be an application level message for uplink RRC messagetransmission. As another example, the F3AP message transmitted by theIAB 1 node to the donor base station via the F3 interface may includeone or more information of signaling bearer types (e.g., SRB0, SRB1, orSRB2) and the UE identifier in addition to the RRC connection requestmessage. As an example, the message transmitted to the donor basestation by the IAB 1 node may include the C-RNTI. Alternatively, the UEidentifier may be one or more information of the valid C-RNITtransmitted to the IAB 1 node by the UE, the RA-RNTI included when theUE transmits the random access preamble for contention-based randomaccess, the temporary C-RNTI allocated via a random access responsemessage by IAB 1, RA-RNTI information identified via the random accessresponse message by IAB 1, and the UE's C-RNTI. Accordingly, the donorbase station may obtain the C-RNTI allocated by the UE's access IAB nodeand uniquely identify the UE along with the IAB node information and/orcell identification information and control the radio resources. Asanother example, the UE identifier may be the I-RNTI allocated by theIAB 1 node. The I-RNTI may uniquely identify the UE context of the UE asidentification information for identifying the UE in the inactive state.As another example, a new UE identifier (marked “IAB-RNTI” for ease ofdescription) for uniquely identifying the received UE by the donor basestation may be transmitted to the donor base station by the IAB 1 node.The donor base station may uniquely identify the UE via the IAB-RNTI andthe IAB node information. As another example, the message transmittedfrom the IAB 1 node to the donor base station may include IAB UE F3AP IDfor uniquely identifying UE association via the F3 interface.

In contention-based random access, the UE selects the random accesspreamble. Thus, there is the likelihood that one or more UEssimultaneously transmit the same random access preamble. In such a case,it may be not enough to perform identification only by the base stationhaving received the random access preamble. Accordingly, it is necessaryto have an additional contention resolving step. To that end, the IABnode or donor base station may indicate what UE transmission has beenactually received to the UE.

Upon transmitting the MAC PDU via the uplink radio resource allocated bythe random access response, the UE includes the UE identificationinformation in the MAC PDU. If the UE has a valid C-RNTI, C-RNTI MAC CEis included in the MAC PDU. For example, the C-RNTI is included inmessage 3 (MSG3). The IAB 1 node may include the C-RNTI upontransmitting an RRC connection request message to the donor base stationto support centralized control for the radio resources of the connectedIAB nodes. Unless the UE has a valid C-RNTI, a CCCH SDU including theUE's identification information is included in the MAC PDU, e.g., whenthe CCCH message (RRC connection request message) is transmitted.

Thereafter, when the UE detects the C-RNTI via the PDCCH or if the UEreceives the same UE contention resolution identity MAC CEL as the CCCHSDU transmitted before, the UE considers the random access procedure assucceeding.

To that end, as an example, the IAB 1 nodestores/buffers/retains/maintains the RRC connection request message(CCCH-SDU) until receiving the RRC connection setup message from thedonor base station.

As another example, the IAB 1 node may receive the RRC connectionrequest message (CCCH SDU) along with the RRC connection setup messagefrom the donor base station.

As another example, the donor base station stores the UE's C-RNTI, as atemporary C-RNTI, as the UE context. Thereafter, upon receiving the RRCconnection setup complete message from the UE, the temporary C-RNTIvalue is set as the C-RNTI.

As another example, the IAB 1 node stores/buffers/retains/maintains theC-RNTI received from the UE. Thereafter, upon receiving the RRCconnection setup message from the donor base station, the temporaryC-RNTI value is set as the C-RNTI. Upon receiving the RRC connectionsetup complete message from the UE, the temporary C-RNTI value is set asthe C-RNTI.

6) To 7) Configuration of Signaling Radio Bearer for Transmission ofControl Message of the UE or IAB Node in IAB 1 Node/IAB 2 Node

The donor base station may configure SRB1 for the UE which hastransmitted the RRC connection request message to the IAB 1 node/IAB 2node, and the donor base station may transmit data (RRC message) betweenthe donor base station and the UE via the signaling radio bearer. Tothat end, the donor base station may configure configuration informationnecessary for the IAB 1 node/IAB 2 node in the IAB 1 node/IAB 2 node.

For example, the configuration information may include mappinginformation for mapping data per signaling radio bearer of each UE tothe radio bearer/radio link control (RLC) bearer between the interfacesand transmitting the same.

As an example, the donor base station may configure SRB1 between thedonor base station and the IAB 1 node for transmission of the F3APmessage of the IAB 1 node and the RRC message of the UE to the IAB 1node which is the UE's access IAB node and transmit the UE's RRC messageand the F3AP message of the IAB 1 node to the donor base station via thesignaling radio bearer. As another example, the donor base station mayconfigure SRB1 between the donor base station and the IAB 2 node fortransmitting the F3AP message of the IAB 2 node and for transmitting theRRC message of the IAB 1 node to the IAB 2 node which is the IAB 1node's access IAB node and transmit the IAB 1 node's RRC message and theF3AP message of the IAB 2 node to the donor base station via thesignaling radio bearer. As another example, the donor base station maytransmit an RRC message or F3AP message, including mapping informationfor mapping the RRC message of the UE to SRB1 between the IAB 1 node andthe donor base station and transmitting the same, to the IAB 1 node,which is the UE's access IAB node, via the signaling radio bearer. Asanother example, the donor base station may transmit an RRC message orF3AP message including the mapping information between the lead-out RLCchannel transmitted to the donor base station and the lead-in RLCchannel including the UE's RRC message received from the IAB 1 node tothe IAB 2 node which is the access IAB node of the IAB 1 node. Thus, itis possible to transmit each UE's RRC message separately between the IAB1 node and the IAB 2 node and between the IAB 2 node and the donor basestation.

As necessary, step 6 and step 7 may be performed simultaneously with, orafter step 8.

8) Transmission of RRC Connection Setup Message from Donor Base Stationto UE

The donor base station transmits the RRC connection setup message to theUE via the IAB 2 node and IAB 1 node. The RRC connection setup messagetransmitted to the UE by the donor base station may be transmitted tothe IAB 1 node or IAB 2 node via the SRB. The RRC connection setupmessage may be included in the F3AP control message between the donorbase station and the IAB 1 node and be transmitted to the IAB 1 node viathe SRB.

9) Transmission of RRC Connection Setup Complete Message from UE toDonor Base Station Via IAB 1 Node

If the CCCH SDU is included in MSG3, if PDCCH transmission has beenaddressed by the UE's temporary C-RNTI, if the MAC packet data unit(PDU) has been successfully decoded, and if the UE contention resolutionidentity in the MAC CE matches the CCCH SDU transmitted in MSG3, the UEconsiders the contention resolution as successful. The UE sets thetemporary C-RNTI as the C-RNTI.

The UE transmits an RRC connection setup complete message to the donorbase station via the IAB 1 node. The RRC connection setup completemessage may be transmitted from the IAB 1 node to the IAB 2 node ordonor base station via the SRB. In this case, the RRC connection setupcomplete message may be included in the F3AP message and be transmittedvia the SRB.

Meanwhile, if the UE identifier is used as the C-RNTI (16 bits), thechance of collision is very low. Thus, the C-RNTI allocated by the IAB 1node may be used as an example of the above-described UE identifier.However, there is also the possibility that theduplicated/collided/contended C-RNTI is used in the cells provided bymultiple IAB nodes received in the donor base station. To preventcollision, the node identifier may be used along with the UE identifierallocated by the IAB 1 node or the C-RNTI as the UE identifier. The nodeidentifier may be allocated when the IAB node configures a connection tothe donor node/attempts access. The node identifier may be allocated tothe IAB node via the RRC message by the donor base station.

When the UE accesses the donor base station via the multi-hop IAB node,the IAB nodes should be able to effectively separate, process andtransfer user data traffic between the UE and the donor base station. Asan example, the IAB node is required to be able to determine a next hopto be able to transfer the uplink data belonging to a specific radiobearer received from a specific UE to the donor base station and forwardthe data to the next hop.

As another example, the IAB node is required to be able to determine anext hop to be able to separately process/transfer the downlink databelonging to a specific radio bearer received from a specific donor basestation to the UE and forward the data to the next hop.

10) Core Network Signaling

The donor base station performs signaling with the core network entityif the RRC connection configuration with the UE is completed. Forexample, the donor base station sends an NGAP initial UE message to thecore network via the NG interface between base station and AMF tothereby receive the initial UE context setup message and performs a corenetwork signaling procedure, such as configuring a UE context. By sodoing, it receives PDU session ID, S-NSSAI, QFI (QoS flow Indicator),QFI-associated QoS profile information to be configured in the UE 900from the core network entity. For this, one of any signaling messagesset forth in the 3GPP TS 38.413 NGAP protocol may be used.

11) To 12) Configuration of Data Radio Bearer for UE in IAB 1 Node/IAB 2Node

In configuring the data radio bearer (DRB) with the UE and transmittingand receiving data, the donor base station may configure configurationinformation necessary for the IAB 1 node/IAB 2 node in the IAB 1node/IAB 2 node. The UE is the UE which has transmitted the RRCconnection request message and transmits/receives data with the donorbase station via the configured DRB.

To that end, the configuration information configured in the IAB 1 nodeand/or the IAB 2 node may include mapping information for mapping dataper data radio bearer of each UE to the radio bearer/RLC bearer betweenthe interfaces and transmitting the same. For example, there may beincluded mapping information for mapping the data per data radio bearerfor each UE to the interface between the IAB 1 node and the IAB 2 nodeand the interface between the IAB 2 node and the donor base station andtransmitting the same. The information may be indicated to the IAB nodevia the F3AP message between the donor base station and the IAB node.

Steps 11 and 12 may be performed simultaneously with, or after, step 13.

13) To 14) Configuration of Radio Resource in UE Via RRC ConnectionReconfiguration Procedure

The donor base station configures radio resources (e.g., radio bearerconfiguration) in the UE via the RRC connection reconfiguration message.The UE sends an acknowledgement message in response thereto.

As described above, the UE, IAB nodes, and the donor base stationconfigure a controller via a relay operation and transmit and receiveRRC messages.

The operation of transferring the UE's RRC message to the donor basestation by the relay node (IAB node) is described below in greaterdetail. For example, the RRC message transmitted by the UE may betransferred to the donor base station via the signaling radio bearer ormay be included in an F3AP message and be transmitted. In the presentembodiment, the description focuses primarily on uplink RRC messages butmay also be applicable to downlink RRC messages. Further, in thefollowing description, as the relay node, the above-described IAB nodeis described, but embodiments of the disclosure are not limited thereto.

FIG. 10 is a flowchart illustrating the operation of transferring an RRCmessage by a relay node according to an embodiment.

Referring to FIG. 10, the relay node may perform configuring a signalingradio bearer or higher layer protocol connection with the donor basestation in a method of processing an RRC message (S1000). The relay nodemay configure a connection with the donor base station and configure asignaling radio bearer. Alternatively, the relay node may configure ahigher layer protocol connection with the donor base station. As anexample, the higher layer protocol connection may be referred to as anF3 application protocol (F3AP).

For example, a relay node denotes an integrated access and backhaul(IAB) node that is connected with the UE via radio access and isconnected with another relay node or donor base station via radiobackhaul. Or, the relay node may mean an IAB node connected with anotherrelay node or donor base station via radio backhaul. In other words, therelay node may be an IAB node performing direct connection via radioaccess with the UE or may be an IAB node that is positioned in themiddle of the relay path or on a side surface of the donor base stationand is not directly connected with the UE.

The relay node may receive mapping information from the donor basestation to configure a signaling radio bearer or higher layer protocolconnection. For example, the relay node may configure a connection usingthe mapping information between the backhaul RLC channel and the UE'slogical channel identification information received from the donor basestation.

The configured signaling radio bearer is ciphered by the PDCP entity ofthe donor base station and the PDCP entity of the relay node.

Meanwhile, the relay node may perform receiving the RRC messagetransmitted from the UE (S1010). For example, the relay node receivesthe RRC message via radio access with the UE.

The relay node may perform transmitting the RRC message to the donorbase station or another relay node using the signaling radio bearer orhigher layer protocol (S1020). For example, the relay node may add theaddress information for the donor base station to the F3AP messageincluding the RRC message and transmit the same, by the adaptationentity of the relay node. Here, the address information for the donorbase station may mean a GPRS tunneling protocol (GTP) tunnel endpointidentifier (TEID) or a donor base station IP address received from thedonor base station.

Further, the RRC message received from the UE may be added to thepayload of the F3AP message and be transmitted via the signaling radiobearer. Besides, the F3AP message may further include at least one of UEidentification information and signaling radio bearer identificationinformation.

Accordingly, the relay node includes the UE's RRC message in the payloadof F3AP and transfers the same to the donor base station via thesignaling radio bearer. Further, for transmission via the signalingradio bearer, the donor base station performs ciphering by the PDCPentity.

FIG. 11 is a view illustrating an exemplary protocol structure fortransferring an RRC message according to an embodiment.

Referring to FIG. 11, the donor base station 1130 is assumed to have asplit structure of a CU and a DU. However, the present embodiments arenot limited thereto. For example, the donor base station 1130 may nothave the split structure. That is, the donor base station 1130 is notlimited to a specific structure.

The RRC and PDCP of the UE 1100 are connected to the RRC and PDCP layerof the donor base station 1130, and the RLC of the UE 1100 is associatedwith the RLC layer of the IAB 2 node 1110. The UE 1100 transmits the RRCmessage to the lead-in RLC entity of the IAB 2 node 1110 via the RLCentity associated with the SRB between the UE 1100 and the donor basestation 1130. The IAB 2 node 1110 is associated with the donor basestation 1130 via F3-AP and transfers the RRC message of the UE 1100 tothe IAB 1 node 1120 via the SRB. The IAB 1 node 1120 is associated withthe donor base station via the backhaul RLC channel and transfers theRLC message of the UE 1100.

As necessary, the IAB 2 node 1110 and the IAB 1 node 1120 separatelyprocess the RRC message transferred, including the adaptation entity.The RRC message may be included in the payload of the F3AP message andbe transferred via the SRB.

FIG. 12 is a signal flow chart illustrating a procedure for transferringan RRC message to a base station according to an embodiment. In FIG. 12,the mobile terminate (MT) part of the IAB 2 node is connected andconfigured in the donor base station. Thus, on the IAB 1 node side, theIAB 2 node may be recognized like the UE and the above-described RRCmessage transfer procedure may be applied.

The IAB nodes may be divided into the MT part and the DU part, and theMT part is recognized as a function similar to the UE from a point ofview of the donor base station or the connected IAB node. The DU part isrecognized as a function similar to the DU base station from a point ofview of the UE or connected IAB node. As described above, the DU basestation denotes a logical node hosting the RLC, MAC, and PHY layers.

Referring to FIG. 12, the IAB 1 node 1210 receives an RRC connectionrequest message from the IAB 2 node 1200 (S1230). The IAB 2 (1200) MTpart performs normal cell discovery and cell selection and transmits an“RRC connection request” to the IAB 1 (1210) DU part. The RRC message isencapsulated as in 1231, and payload 1 transmitted to the donor basestation includes PDCP and RLC data (e.g., the IAB-node2 MT part performsnormal cell discovery and cell selection and sends “RRC connectionrequest” to IAB-node1 DU part).

The IAB 1 (1210) DU part receives a payload 1 transmitted from the IAB 2(1200) MT part. The Payload 1 denotes the PDCP PDU including the RRCmessage. The DU part of the IAB 1 node 1210 generates an F3AP message(i.e., initial UL RRC message) for carrying payload 1 (S1235) (IAB-node1DU part generates F3AP message (i.e. the initial UL RRC Message) tocarry the RRC message sent from IAB-node2 MT part).

The MT part of IAB 1 1210 (e.g., the IAB I MT part) transmits theencapsulated uplink F3AP message to the donor base station 1220 via theSRB (S1240)(e.g., the IAB-node1 MT part transmits the encapsulateduplink F3AP message to Donor-DU via SRB). The uplink F3AP message 1241further includes IAB 2(1200) F3AP UE ID, and Adaptation layer. Payload 2of 1241 includes PDCP, F3AP, and payload 1.

The DU 1221 of the donor base station 1220 recognizes a specific messagetype (F3AP message of IAB node). Then, the DU 1221 removes the header ofthe adaptation layer and encapsulates payload 2 (including the F3APmessage of IAB node) in its own F3AP message (S1245)(Donor-DU learns thespecific message type (F3AP message of IAB-node). Then the DU 1221removes the header of adaptation layer, and encapsulates the payload2(including the F3AP message of IAB-node) in its own F1AP message).

The DU 1221 of the donor base station 1220 transmits the F3AP message1251, including the F3AP message of IAB 1 1210, to the CU 1222 of thedonor base station 1220 (S1250)(Donor-DU sends its F1AP message whichcontains the IAB-node1's F3AP message towards the donor-CU).

The CU 1222 of the donor base station 1220 obtains payload 2 afterdecapsulating the F3AP message 1251 received from the DU 1221 of thedonor base station 1220. The CU 1222 of the donor base station 1220obtains the “RRC connection request” message in payload 2 via additionaldecapsulation (S1255)(After decapsulation of the F1AP message receivedfrom Donor-DU, Donor-CU get payload2, and obtains the “RRC connectionrequest” message inside payload2 through further decapsulation).

The CU 1222 of the donor base station 1220 transmits the F3AP message(e.g., DL IAB F3AP message transmission) including payload 2 and routinginformation about payload 2 (e.g., IAB 1 address or donor base stationCU address) to the DU 1221 of the donor base station 1220 (S1260)(Donor-CU sends the F1AP message (e.g. DL IAB F1AP message transfer)which contains payload2 towards the Donor-DU and routing information(e.g., IAB-node 1 address, Donor-CU address, etc.) for the payload2).

The DU 1221 of the donor base station 1220 extracts payload 2 from thereceived F3AP message (e.g., DL IAB F1AP message) and adds theadaptation layer header including essential routing information forpayload 2 (S1265)(Donor-DU extract payload2 from the received F1APmessage (e.g. DL IAB F1AP message transfer), and adds the adaptationlayer header which includes essential routing information for payload2).

The DU 1221 of the donor base station 1220 transmits the encapsulateddownlink F3AP message (transmission of DL RRC message in payload 2) tothe IAB 1 (1210) MT part via the SRB (S1270)(Donor-DU transmits theencapsulated downlink F3AP message (DL RRC message transfer, insidepayload2) towards IAB-node1 MT part via SRB).

The MT part of IAB 1 1210 recognizes a specific message type (F3APmessage of IAB node) according to a specific SRB or message typeindicator and identifies that the F3AP message, as adaptation headerrouting information, is for its own. Thereafter, the IAB 1 (1210) MTpart removes the header of the adaptation layer and, after receiverprocessing of the PDCP layer, transfers the F3AP message including theRRC message for IAB 2 1200 to the IAB 1 (1210) DU part (S1280)(IAB-node1MT part learns the specific message type (F3AP message of IAB-node)according to the specific SRB or the message type indicator, and knowsthat the F3AP message is for itself from the routing information in theadaptation header. Then IAB-node 1 MT part removes the header ofadaptation layer, and forwards the F3AP message which contains the RRCmessage for IAB-node 2 after receiver processing of the PDCP layer toIAB-node 1 DU part. The IAB-node 1 DU part extracts the RRC message fromF3-AP message).

The DU part of IAB 1 1210 extracts the RRC message from the F3AP message(IAB-node1 DU parts send the RRC message (RRC connection setup) towardsIAB-node 2).

As described above, the relay node includes the RRC message in the F3APmessage and transfers the same to the donor base station via the SRB.

Hereinafter, a relay node protocol structure supporting theabove-described operations will be described. For ease of description,uplink data transmission operations for a user plane protocol structureare described below. However, the present embodiments are not limitedthereto. For example, the same method is applicable to control planeprotocol structures. Although a protocol structure via two hops isdescribed below, any structure via any number of hops falls within thecategory of the disclosure.

FIG. 13 is a flowchart illustrating an operation of transferring uplinkuser data by a relay node according to an embodiment.

Referring to FIG. 13, the relay node may perform receiving uplink userdata from the UE in a method of processing uplink user data (S1300). Asdescribed above, relay node maybe an integrated access and backhaul(IAB) node that is connected with the UE via radio access and isconnected with another relay node or donor base station via radiobackhaul. Or, the relay node may denote an IAB node connected withanother relay node via radio backhaul and connected with the donor basestation via radio backhaul. The relay node receives uplink user datawhich is transmitted to the donor base station from the UE.

The relay node may perform deriving a UE bearer identifier(UE-bearer-ID) using logical channel identification informationassociated with the RLC PDU of the uplink user data (S1310). Uponreceiving the uplink user data, the relay node extracts the UE beareridentifier using the logical channel identification informationassociated with the RLC PDU. That is, the relay node may identify the UEbearer identifier using the logical channel identification information.As an example, the UE bearer identifier may denote the PDU session IDand QoS flow indicator (QFI) indicated to identify the UE's bearer fromthe donor base station. As another example, the UE bearer identifier mayindicate the radio bearer identifier (drb-identity) indicated toidentify the UE's bearer from the donor base station. As anotherexample, the UE bearer identifier may indicate the GPRS tunnelingprotocol (GTP) tunnel endpoint identifier (TEID) allocated and indicatedto identify the UE's bearer from the donor base station.

The relay node may perform selecting the backhaul RLC channel fortransmitting uplink user data based on at least one of the UE beareridentifier and donor base station address information (S1320). Forexample, the relay node may select the backhaul RLC channel mapped tothe UE bearer identifier using the derived UE bearer identifier. Or, therelay node may select the backhaul RLC channel for transmitting uplinkuser data using the donor base station address information. As anexample, the donor base station address information may be a GPRStunneling protocol (GTP) tunnel endpoint identifier (TEID) or a donorbase station IP address received from the donor base station. That is,the relay node may previously receive and store the donor base stationaddress information.

Meanwhile, the relay node may select the backhaul RLC channel based onthe backhaul RLC channel mapping information included in the UE's UEcontext setup message received from the donor base station. That is, thebackhaul RLC channel mapping information is required to select thebackhaul RLC channel using at least one of the above-described UE beareridentifier and donor base station address information. The relay nodemay receive the backhaul RLC channel mapping information from the donorbase station.

For example, the backhaul RLC channel mapping information may includeN:1 (N is a natural number not less than 1) mapping information betweenthe backhaul RLC channel and at least one of the UE bearer identifierand donor base station address information. Or, the backhaul RLC channelmapping information may include mapping information between the UEbearer identifier and donor base station address information.

Meanwhile, the backhaul RLC channel may be configured according to thelogical channel configuration information of the RRC message. That is,the relay node may configure the backhaul RLC channel using the logicalchannel configuration information of the RRC message.

The relay node may perform transmitting the uplink user data to thedonor base station or another relay node via the selected backhaul RLCchannel (S1330). The relay node may include at least one information ofthe UE bearer identifier, donor base station address information,logical channel identification information, and mapping informationbetween the backhaul RLC channel and the logical channel identificationinformation, in the uplink user data and transmit the same, by theadaptation entity of the relay node. For example, the relay node may addUE bearer identifier information to the uplink user data in transmittingthe uplink user data via the backhaul RLC channel. Adding the UE beareridentifier information may be performed by the adaptation entity of therelay node. Or, the donor base station address information and theabove-described mapping information may be included in the transmitteduplink user data so that the donor base station or another relay nodemay utilize the information.

Meanwhile, the relay node may further include, before receiving uplinkuser data from the UE, receiving an RRC connection request message fromthe UE and transmitting the RRC connection request message to the donorbase station via a signaling radio bearer or F3AP message. As describedabove in connection with FIGS. 10 to 12, the relay node may include theUE's RRC message in the F3AP message and transfer the same via the SRB.The signaling radio bearer or F3AP message may be configured to includedonor base station address information in the adaptation entity.

As described above, upon receiving the uplink user data transmitted tothe donor base station from the UE, the relay node may separatelyprocess uplink user data using various pieces of information, such aslogical channel identification information or mapping information. Thatis, the relay node determines the donor base station or another relaynode for transferring the uplink user data and transmits the same viathe selected backhaul RLC channel.

Various example protocols for transferring uplink user data aredescribed below with reference to the drawings. For ease of description,the relay node is denoted an IAB node below.

FIG. 14 is a view illustrating an exemplary protocol structure fortransmitting uplink user data according to an embodiment.

Referring to FIG. 14, a IAB 2 node 1410 receives uplink user data fromthe UE 1400 via a DRB. The IAB 2 node 1410 derives a UE beareridentifier using logical channel identification information associatedwith the RLC PDU of the received uplink user data. Further, the relaynode selects a backhaul RLC channel for transmitting uplink user databased on at least one of the UE bearer identifier and donor base stationaddress information.

The received uplink user data is transferred to the IAB 1 node 1420 viathe MT part. To transmit the uplink user data to the IAB 1 node 1420,the IAB 2 node 1410 selects the backhaul RLC channel. Further, the IAB 2node 1410 may further include at least one information of UE beareridentifier, address information for the donor base station 1430, logicalchannel identification information, and mapping information betweenlogical channel identification information and backhaul RLC channel inthe uplink user data transmitted to the IAB 1 node 1420.

The IAB 1 node 1420 transfers the message including the uplink user datareceived from the IAB 2 node 1410 to the DU 1431 of the donor basestation 1430. The DU 1431 of the donor base station 1430 transfers tothe CU 1432 via the IP layer.

FIG. 15 is a view illustrating an exemplary protocol structure fortransferring uplink user data from a single-structure donor base stationaccording to an embodiment.

The protocol structure of FIG. 14 is identically applied to a UE 1400, aIAB 2 node 1410, and a IAB 1 node 1420 in FIG. 15. However, the donorbase station 1500 may not have a split structure of a CU and a DU. Thatis, the donor base station may perform the operations from the SDAPlayer to the MAC layer in one logical node. Besides, the transmissionpath and operations of uplink user data are the same as those of FIG.14, and no description thereof is given below.

Protocol Structure Embodiment for Performing L3 Forwarding in IAB Node

FIG. 16 is a view illustrating an exemplary protocol structure fortransmitting uplink user data according to an embodiment.

Referring to FIG. 16, (each) IAB nodes 1610 and 1620 may forward userdata by L3 (IP layer) similarly to the typical LTE RN. To that end, thefirst hop IAB node (IAB-1) 1610 having a direct radio connection withthe UE 1600 needs to support the functions of layer 3 or higher layers,as well as the functions of layer 2. For example, the IAB 1 node 1610may configure/reconfigure radio connection parameters in the UE 1600 viaan RRC connection reconfiguration message. Accordingly, the IAB 1 node1610 supporting layer 3 may control the cell with the cell identifierwhich the IAB 1 node 1610 owns and may allow it to look to the UE 1600like a normal base station. However, in this case, in processing userdata, delay for IP packet processing in addition to layer 2 processingmay be increased.

User data forwarding between IAB nodes (e.g., the IAB 1 node and the IAB2 node) may be performed via GTP-U (or GTP-U/UDP/IP. For control planedata, GTP-C or GTP/SCTP protocol is used). Accordingly, trafficprocessing separated/differentiated per user or per radio bearer (or perflow) may be possible. As an example, the IAB node 1610 or 1620 maydifferentiate each data traffic via the GTP TEID. To that end, the IABnode 1610 or 1620 may previously receive the GTP-TEID and donor basestation IP address as the donor base station address information.Typically, the GTP-TEID is information for unequivocally identifying thetunnel endpoint in the receive GTP-U protocol entity, and the TEID to beused on the transmit side of the GTP tunnel is locally allocated on thereceive side of the GTP tunnel. In each network node, one GTP-U tunnelis identified with one TEID, one IP address, and one UDP port number.The TEID indicates the tunnel where the user data, which becomes thepayload in the GTP-U tunnel, belongs.

In the present embodiment, the donor base station may allocate the TEIDmapped to the UE bearer identifier and transfer the same, along with thedonor base station IP address, to the access IAB node serving the UE. Atthis time, the TEID and IP address may be transferred via the RRCmessage or F3AP message.

As another example, the IAB node 1610 or 1620 may differentiate eachdata traffic (e.g., user data) via mapping information for one or moreof GTP TEID, PDU session ID, S-NSSAI, QFI (QoS flow Indicator),associated QoS profile (e.g. 5QI, allocation and retention priority),DSCP, drb-identity and SRB type. As an example, the IAB node 1610 or1620 may receive uplink user data associated with the UE's QFI and PDUsession ID from the UE 1600, map the received uplink user data to theGTP-TEID, and separately transmit the results to the donor base station.

User data forwarding between the IAB node 1610 or 1620 and the donorbase station DgNB may be performed via GTP-U (or GTP-U/UDP/IP. Forcontrol plane data, GTP-C or GTP/SCTP protocol is used). Accordingly,traffic processing separated/differentiated per user or per radio bearer(or per flow) may be possible. As an example, each data traffic may bedifferentiated via the GTP TEID. As another example, each data trafficmay be differentiated via mapping information for one or more of GTPTEID, PDU session ID, S-NSSAI, and QFI.

As an example, the above-described mapping information may be indicatedto the IAB node via OAM. As another example, the above-described mappinginformation may be indicated to the IAB node via the RRC message by thedonor base station. As another example, the above-described mappinginformation may be indicated to the IAB node via the F3AP message by thedonor base station. As another example, the above-described mappinginformation may include mapping information between one or more piecesof information of E-RAB, PDU session resource information (e.g., PDUsession ID, S-NSSAI), QFI/QCI, QFI-associated QoS profile, DSCP(Diffserv code point), TEID, Transport layer Address (e.g., donor basestation IP address), drb-identity and SRB type. Specifically, as anexample, QFI and transport layer information (TEID, transport layeraddress) mapping information may be included. Or, mapping informationbetween DSCP and radio bearer identification information (drb-identityor SRB type) may be included. Or, mapping information between QFI andradio bearer identification information (drb-identity or SRB type) maybe included. Thus, the field including one or more pieces of informationof PDU session resource information included in the GTP-U header (e.g.,PDU session ID, S-NSSAI), QFI/QCI, QFI-associated QoS profile, DSCP(Diffserv code point), TEID, Transport layer Address (e.g., donor basestation IP address), drb-identity and SRB type is associated with oneflow/bearer on the interface between IAB nodes or the interface betweenthe IAB and the donor base station. One or more pieces of information ofPDU session resource information (e.g., PDU session ID, S-NSSAI),QFI/QCI, QFI-associated QoS profile, DSCP (Diffserv code point), TEID,Transport layer Address (e.g., donor base station IP address),drb-identity and SRB type may be used to identify the radio bearer ofthe radio interface between the UE and the IAB node. As an example, theIAB node 1610 or 1620 may receive uplink user data associated with theUE's QFI and PDU session ID from the UE 1600, map the received uplinkuser data to the GTP-TEID and donor base station IP address, andseparately transmit the results to the donor base station.

Protocol Structure Embodiment for Performing L3 Forwarding in First HopIAB Node Connected with UE and L2 Forwarding in Other IAB Node

FIG. 17 is a view illustrating an exemplary protocol structure fortransmitting uplink user data according to an embodiment.

Referring to FIG. 17, the first hop IAB node 1710 configuring a directradio connection with the UE 1600 may forward user data from L3 (IPlayer), similar to the typical LTE RN. To that end, the first hop IABnode (IAB-1) 1710 having a direct radio connection with the UE 1600needs to support the functions of layer 3 or higher layers, as well asthe functions of layer 2. For example, the IAB 1 node 1710 mayconfigure/reconfigure radio connection parameters via an RRC connectionreconfiguration message. Accordingly, the IAB 1 node 1710 supportinglayer 3 may control the cell with the cell identifier which the IAB 1node 1610 owns and may allow it to look to the UE 1600 like a normalbase station. However, in this case, delay for IP packet processing inaddition to layer 2 processing may be increased.

User data may be transferred via the GTP-U (or GTP-U/UDP/IP. For controlplane data, GTP-C or GTP/SCTP protocol is used) protocol between thedonor base station 1730 and the first hop IAB node 1710 with a directradio connection with the UE 1600. As an example, the donor base station1730 and the first hop IAB node 1710 with a direct radio connection withthe UE 1600 may perform traffic processing separated/differentiated peruser or per radio bearer (or per flow) via the GTP TEID. As anotherexample, the IAB node 1710 and the donor base station 1730 maydifferentiate per-user, per-radio bearer traffic via the mappinginformation for one or more of the GTP TEID, Transport layer Address(e.g., donor base station IP address), PDU session ID, S-NSSAI, QFI (QoSflow Indicator), QFI-associated QoS profile, DSCP, drb-identity and SRBtype. As an example, the first hop IAB node 1710 may receive uplink userdata associated with the UE's QFI and PDU session ID from the UE 1600,map the same to the GTP-TEID and donor base station IP address, andseparately transmit the results to the donor base station. As anotherexample, if the first hop IAB node 1710 separately forwards user data onthe RLC layer as shown in FIGS. 18 and 19, the first hop IAB node 1710may receive uplink user data associated with the logical channelidentification information mapped to the UE bearer identifier or theUE's PDU session ID and QFI from the UE 1600 and map the same to theGTP-TEID and donor base station IP address and separately transmit theresults to the donor base station.

Meanwhile, user data forwarding by an IAB node (IAB 2, 1720), not thefirst hop IAB node 1710 having a direct radio connection with the UE1600, may be performed on the L2 basis. As an example, user data may beforwarded from the SDAP layer as shown in FIG. 17. Accordingly, it ispossible to perform data forwarding meeting per-flow QoS. Each QoS flowmay perform its corresponding data forwarding processing via itscorresponding QoS parameter/profile (e.g., one or more parameters of 5GQoS Identifier, Allocation and Retention Priority, Guaranteed Flow BitRate, Maximum Flow Bit Rate, and Reflective QoS Attribute) and may bemapped to the DRB according to the QoS profile associated with the QFI(QoS flow Indicator). However, since the IAB 2 node 1720 may notdifferentiate data per UE, the transmit SDAP entity or the adaptationlayer entity higher than the SDAP may add the UE identifier fordifferentiation for each UE and transmit the same. The mapped flow/datamay be selected based on the UE identifier added by the IAB 2 node 1720.The receive SDAP entity or the adaptation layer entity higher than theSDAP may remove the UE identifier for per-UE differentiation andtransmit the same to the higher layer.

Or, the IAB 2 node 1720 of FIG. 17 may be operated without the SDAPlayer. That is, the IAB 2 node 1720 may forward user data from the PDCPlayer. Accordingly, data forwarding for differentiating radio bearersmay be performed, and ciphering and/or integrity protection may beprovided from each link. However, since the IAB 2 node 1720 is incapableof per-UE differentiation, the transmit SDAP entity, or the adaptationlayer entity between the SDAP and PDCP entities, or the PDCP entity mayadd the UE identifier for per-UE differentiation and transmit and, basedthereupon, the IAB 2 node 1720 may select the mapped radio bearer. Thereceive SDAP entity, the adaptation layer entity between the SDAP andPDCP entities, or the PDCP entity is required to remove the UEidentifier for per-UE differentiation and transmit the same to thehigher layer.

Or, the IAB 2 node 1720 of FIG. 17 may be operated without the SDAPlayer and PDCP layer. The user data may be forwarded from the adaptationlayer over the RLC, the RLC layer, the adaptation layer over the RLClayer and MAC layer, or the MAC layer. Therefore, it is possible toperform data forwarding to differentiate radio bearer/RLC bearer/logicalchannel. However, since the IAB 2 node 1720 is unable to perform per-UEdifferentiation, the adaptation layer entity over the transmit RLC, theRLC layer entity, the adaptation layer entity over the RLC layer and MAClayer, or the MAC entity may add the UE bearer identifier for per-UEdifferentiation and transmit the same. The IAB 2 node 1720 selects themapped radio bearer based on the UE bearer identifier, and theadaptation layer entity over the receive RLC of the donor base station1730, the RLC layer entity, the adaptation layer entity over the RLClayer and the MAC layer, or the MAC entity is required to remove the UEbearer identifier for per-UE differentiation and transmit the same tothe higher layer.

Or, L2 forwarding by the IAB 2 node 1720 may be provided by referring tothe embodiments (L2 forwarding by IAB node-1, and L2 forwarding by IABnode-2) described below. The following embodiments are described belowin detail.

Protocol Structure Embodiment for L2 Forwarding by IAB Node-1(Adaptation Layer Higher than RLC is Applied)

FIG. 18 is a view illustrating an exemplary protocol structure fortransmitting uplink user data according to an embodiment. FIG. 19 is aview illustrating an exemplary protocol structure for transmittinguplink user data according to an embodiment.

Referring to FIG. 18, the IAB node 1810 or 1820 may differentiate andforward user data on the layer 2 entity (sublayer 2 entity).

As an example, the IAB node 1810 or 1820 may differentiate and forwarduser data on the RLC layer. As another example, as shown in FIG. 18, theIAB node 1810 or 1820 may place the adaptation layer over the RLC layerand separately forward the user data on the adaptation layer. As anotherexample, as shown in FIG. 19, the IAB node 1910 or 1920 may place theadaptation layer under the RLC layer (or over the MAC layer) andseparately forward the user data on the RLC layer.

Hereinafter, a method of the UE for transmitting uplink data to thedonor base station via the IAB node according to an embodiment will bedescribed for ease of description. However, the embodiments of thepresent disclosure are not limited thereto. For example, the embodimentsmay be applied to downlink data transmission.

If an adaptation layer exists on the RLC layer as shown in FIG. 18, itis necessary to map the per-UE RLC bearer (or radio bearer) (for uplinkdata) to the RLC bearer (or radio bearer) between the donor base station1830 and the IAB node 1810 or 1820 or the RLC bearer (or radio bearer)on the interface between IAB nodes (IAB 1 and IAB 2) on the adaptationlayer entity of the first hop IAB node (IAB 1) 1810 enabling a directradio connection with the UE 1600. Here, the RLC bearer (RLC channel)indicates a lower layer portion of the radio bearer configurationconsisting of the RLC and logical channel. It indicates the logicalconnection or channel between the transmit RLC entity of the IAB 1 nodeand the receive RLC entity of IAB 2 on, e.g., the radio backhaulinterface between the IAB 1 node and the IAB 2 node in uplink datatransmission via the IAB node. For ease of description, the terms “RLCbearer” and “radio bearer” may be interchangeably used herein. Forexample, RLC bearer may be referred to as a radio bearer, and radiobearer may be referred to as a RLC bearer. The RLC bearer may bereplaced with the radio bearer, and the radio bearer may be replacedwith the RLC bearer.

If there is no restriction on the number of RLC bearers (or radiobearers) providable on the interface between IAB nodes (IAB 1 and IAB 2)or the interface between the IAB node and the donor base station(between IAB 2 and DgNB), the per-UE RLC bearers (or radio bearers) onthe adaptation layer entity of the first hop IAB node (IAB 1) having adirect radio connection with the UE and the RLC bearers (or radiobearers) on the interface between IAB nodes (between IAB 1 and IAB 2)may be configured to be mapped in a one-to-one manner. As an example,the one-to-one mapping configuration may be made by the donor basestation via an RRC message to the IAB 1 node. As another example, theone-to-one mapping configuration may be made by the donor base stationvia an F3AP message to the IAB 1 node. As another example, theone-to-one mapping configuration may be made as the OAM indicatesmapping information to the IAB 1 node.

Or, per-RLC bearers (or radio bearers) and RLC bearers (or radiobearers) between the IAB node and the donor base station (between IAB 2and DgNB) may be configured to be mapped in a one-to-one manner. As anexample, the one-to-one mapping configuration may be made as the donorbase station transmits an RRC message to the IAB 2 node. As anotherexample, the one-to-one mapping configuration may be made by the donorbase station via an F3AP message to the IAB 2 node. As another example,the one-to-one mapping configuration may be made as the OAM indicatesmapping information to the IAB 1 node.

If there is a restriction on the number of RLC bearers (or radiobearers) providable on the interface between IAB nodes (IAB 1 and IAB 2)or the interface between the IAB node and the donor base station(between IAB 2 and DgNB), it is necessary to map i) the per-UE RLCbearers (or radio bearers) on the adaptation layer entity of the firsthop IAB node (IAB 2) having a direct radio connection with the UE andthe RLC bearers (or radio bearers) on the interface between IAB nodes(between IAB 1 and IAB 2) or ii) the per-UE RLC bearers (or radiobearers) on the IAB node (IAB 2) in the middle and the RLC bearers (orradio bearers) between the IAB node and the donor base station (betweenIAB 2 and DgNB) in an N:1 manner. Here, N is any natural number.

There is a limit to the maximum number of radio bearers currentlyprovidable between the UE and the base station (or the maximum number ofradio bearers providable by the UE). For example, the maximum number ofDRBs providable is eight in LTE. In NR, the maximum number of DRBsprovidable is at most 32. Thus, in the case where the IAB node receivesmultiple IAB nodes and the UE and relays the same to the donor basestation, if the maximum number of DRBs providable by the IAB node isidentical to the maximum number of DRBs providable by a regular UE, itis necessary to restrict the number of radio bearers/RLC bearers mappedto the radio bearers with the UE capable of relaying between the IABnode and the donor base station or between the IAB node and the IABnode.

For example, assume the following scenario. The IAB 1 node is connectedto UE-1, UE-2, and UE-3, and three radio bearers (radio bearer-1, radiobearer-2, and radio bearer-3) are configured in UE-1. Two radio bearers(radio bearer-a and radio bearer-b) are configured in UE-2. Two radiobearers (radio bearer-A and radio bearer-B) are configured in UE-3. NoUE is directly connected to the IAB 2 node, and no other IAB node thanIAB 1 is directly connected to IAB 2. No UE is directly connected to thedonor base station, and no other IAB node than IAB 2 is directlyconnected thereto.

Under the assumed scenario, for uplink data processing, the number oftransmit RLC entities of UE-1 is three, the number of transmit RLCentities of UE-2 is two, and the number of transmit RLC entities of UE 3is two. The number of receive RLC entities of the peered IAB 1 node isthree (UE-1 peered entity), two (UE-2 peered entity), or two (UE-3peered entity). The donor base station may determine the number oftransmit RLC entities for transmission of data from the IAB 1 node tothe IAB 2 node. For example, the number of radio bearers/RLC bearerscapable of same packet forwarding processing may be determined dependingon the radio bearer/RLC bearer type/attribute to be provided per UE. Asan example, if UE-1's radio bearer-1, UE-2's radio bearer-a, and UE-3'sradio bearer-A are radio bearers capable of same packet forwardingprocessing (e.g., default bearers of the same PDU session or radiobearers providing the same service), the three radio bearers/RLC bearersmay be mapped to one transmit RLC entity from the IAB 1 node to the IAB2 node (or one RLC bearer on the interface between the IAB 1 node andthe IAB 2 node) and data may be processed/transferred. This may beprovided from the adaptation layer entity. Thus, the receive RLC entity(RLC-RX1) peered to the transmit RLC entity (RLC-TX1) of UE-1 radiobearer-1 at the IAB 1 node may be mapped to one transmit RLC entity(marked “RLC entity-11” for ease of description) to the IAB 2 node. Thereceive RLC entity (RLC-RXa) peered to the transmit RLC entity (RLC-TXa)of UE-2 radio bearer-a at the IAB 1 node may be mapped to the sametransmit RLC entity (RLC entity-11) to the IAB 2 node. The receive RLCentity (RLC-RXA) peered to the transmit RLC entity (RLC-TXA) of UE-3radio bearer-A at the IAB 1 node may be mapped to the same transmit RLCentity (RLC entity-11) to the IAB 2 node.

Meanwhile, upon uplink data transmission, the RLC entities (or RLCconfiguration information) in the UE may be differentiated by thelogical channel identification information. Thus, the mapping betweenthe receive RLC entity of the IAB 1 node peered to the RLC entity of aspecific radio bearer/RLC bearer of a specific UE and the transmit RLCentity of the IAB 1 node peered to the receive RLC entity of the IAB 2node may be provided by associating the pieces of logical channelidentification information. As an example, the donor base station mayprovide the same by configuring, in IAB 1, the mapping informationbetween the logical channel identification information of the specificradio bearer/RLC bearer of the specific UE and the logical channelidentification information of the RLC bearer on the radio interfacebetween IAB-1 and IAB 2. This may be indicated from the donor basestation to the IAB-1 node via an RRC message or F3AP message. The donorbase station may indicate the configuration information including themapping information corresponding to the IAB node upon indicating theRRC message to the UE so as to configure the radio resource in the UE.For example, upon transmitting the UE's RRC reconfiguration message tothe UE via the IAB node, the donor base station may also include thecorresponding mapping information to the IAB node via the F3AP messageincluding the corresponding RRC reconfiguration message.

As another method, the RLC entity in the UE may be differentiated by theradio bearer identification information associated with the PDCP entity.As an example, the donor base station may indicate/configure, in the IAB1 node, the mapping information between the radio bearer identificationinformation of the specific radio bearer/RLC bearer of the specific UEand the logical channel identification information (or radio beareridentification information) on the radio interface between the IAB 1node and the IAB 2 node, thereby providing the radio beareridentification information associated with the PDCP entity.

The UE radio bearer identification information associated with the PDCPentity may be included and provided in the adaptation layerconfiguration information on the RRC message for IAB 1 radio resourceconfiguration. Or, the UE radio bearer identification informationassociated with the PDCP entity may be included and provided in the RLCconfiguration information on the RRC message for IAB 1 radio resourceconfiguration. Or, the UE radio bearer identification informationassociated with the PDCP entity may be included and provided in thelogical channel configuration information on the RRC message for IAB 1radio resource configuration. Or, the UE radio bearer identificationinformation associated with the PDCP entity may be included and providedin the F3AP message transmitted to the IAB 1 node. The configurationinformation/mapping information may include the UE identifier, the UE'sradio bearer identifier/logical channel identification information, andlogical channel identification information (or radio beareridentification information) for the RLC bearer on the radio interfacebetween IAB 1 and IAB 2 mapped thereto. The mapping information may beindicated from the donor base station to the IAB 1 node via an RRCmessage or F3AP message. The donor base station may indicate theconfiguration information including the mapping informationcorresponding to the IAB 1 node upon indicating the RRC message to theUE so as to configure the radio resource in the UE. For example, upontransmitting the UE's RRC reconfiguration message to the UE via the IABnode, the donor base station may also include the corresponding mappinginformation to the IAB node via the F3AP message including thecorresponding RRC reconfiguration message.

As another method, in the case where the first hop IAB nodedifferentiates the per-UE radio bearer data via the GTP TEID andtransfers the same to the donor base station as shown in FIGS. 15 to 17,the UE's RLC entity (or RLC configuration information) at the IAB 1 nodemay be mapped to the GTP TEID and be transmitted with the per-UE radiobearers differentiated. The TEID at the IAB 1 node may be mapped to thetransmit RLC entity of the IAB 1 node peered to the receive RLC entityof the IAB 2 node with the GTP TEID and the donor base station IPaddress associated with the logical channel identification information.As an example, the donor base station may indicate/configure, in the IAB1 node, the mapping information between the TEID mapped to the specificradio bearer/RLC bearer of the specific UE, donor base station IPaddress and the logical channel identification information (or radiobearer identification information) on the radio interface between theIAB 1 node and the IAB 2 node. The information may be included andprovided in the adaptation layer configuration information on the RRCmessage for IAB 1 radio resource configuration. Or, the information maybe included and provided in the RLC configuration information on the RRCmessage for IAB 1 radio resource configuration. Alternatively, theinformation may be included and provided in the logical channelconfiguration information on the RRC message for IAB 1 radio resourceconfiguration. Or, the information may be included and provided in theF3AP message transmitted to the IAB 1 node. The configurationinformation/mapping information may include the UE identifier, the TEIDassociated with the UE's radio bearer identifier/logical channelidentification information, donor base station IP address and logicalchannel identification information (or radio bearer identificationinformation) for the RLC bearer on the radio interface between the IAB 1node and the IAB 2 node mapped thereto. The mapping information may beindicated from the donor base station to the IAB 1 node via an RRCmessage or F3AP message. The donor base station may indicate theconfiguration information including the mapping informationcorresponding to the IAB node 1 upon indicating the RRC message to theUE to configure the radio resource in the UE. For example, upontransmitting the UE's RRC reconfiguration message to the UE via the IABnode, the donor base station may also include the corresponding mappinginformation to the IAB node via the F3AP message including thecorresponding RRC reconfiguration message.

In a similar manner to the above-described method, it requiresinformation for mapping the RLC bearer on the interface between the IABnodes (between IAB 1 and IAB 2) (or the RLC bearer (or radio bearer) perUE at the IAB node (IAB 2) positioned in the middle) to the RLC bearer(or radio bearer) between the IAB node and the donor base station(between IAB 2 and DgNB). For example, the donor base station maydetermine the number of radio bearers/RLC bearers capable of same packetforwarding processing at the IAB node (IAB 2) positioned in the middledepending on the radio bearer/RLC bearer type/attribute to be providedper UE. Or, the donor base station may determine the number of radiobearers/RLC bearers capable of same packet forwarding processing at theIAB node (IAB 2) positioned in the middle depending on the radiobearer/RLC bearer type/attribute provided from the IAB node (IAB 1)connected to the lower layer.

Upon uplink data transmission, the RLC entities (or RLC configurationinformation) in the UE may be differentiated by the logical channelidentification information. Thus, the mapping information forinstructing to transmit data belonging to the specific radio bearer/RLCbearer of the specific UE from the IAB node to a next hop IAB node (orthe donor base station if the next hop is the donor base station) may beprovided via the logical channel identification information. As anexample, the donor base station may provide the same by configuring, inthe IAB 2 node, the mapping information between the logical channelidentification information of the specific radio bearer/RLC bearer ofthe specific UE and the logical channel identification information ofthe RLC bearer on the radio interface between IAB 2 and the donor basestation. This may be indicated from the donor base station to the IAB 2node via the RRC message. The donor base station may indicate theconfiguration information including the mapping informationcorresponding to the IAB node upon indicating the RRC message to the UEso as to configure the radio resource in the UE.

As another method, the RLC entity in the UE may be differentiated by theradio bearer identification information associated with the PDCP entity.As an example, the donor base station may provide this byindicating/configuring, in the IAB 2 node, the mapping informationbetween the radio bearer identification information of the specificradio bearer/RLC bearer of the specific UE and the logical channelidentification information (or radio bearer identification information)on the radio interface between the IAB 1 node and the IAB 2 node.

The mapping information may be included and provided in the adaptationlayer configuration information. The mapping information may include theUE identifier, the UE's radio bearer identifier/logical channelidentification information, and logical channel identificationinformation (or radio bearer identification information) for the RLCbearer on the radio interface between the IAB-2 node and the donor basestation, mapped thereto. The IAB-2 node may transfer the data to the MACentity according to the configuration mapping information.

The donor base station adaptation layer entity may transfer the data tothe associated PDCP entity based on the UE identifier and logicalchannel identification information (or radio bearer identificationinformation) included in the received data.

As another example, the mapping information between the logical channelidentification information of the RLC bearer on the radio interfacebetween the IAB 1 node and the IAB 2 node and the logical channelidentification information of the RLC bearer on the radio interfacebetween the IAB 2 node and the donor base station may be configured inthe IAB 2 node. The mapping information may be indicated from the donorbase station to the IAB 2 node via an RRC message or F3AP message. Whenthis is indicated from the donor base station to the IAB 1 node via theRRC message or when the RRC message is indicated to the UE to configurea radio resource in the UE, the configuration information including themapping information corresponding to the IAB 2 node may be indicated viathe F3AP message.

As another method, the RLC entity in the UE may be differentiated by theradio bearer identification information associated with the PDCP entity.As an example, the donor base station may provide the same byconfiguring, in the IAB 2 node, the mapping information between theradio bearer identification information of the RLC bearer on the radiointerface between the IAB 1 node and the IAB 2 node and the logicalchannel identification information (or radio bearer identificationinformation) on the radio interface between the IAB 2 node and the donorbase station. The IAB 2 node may add one or more pieces of informationto the header of the data according to the configuration mappinginformation and transfer the header-added data to the corresponding MACentity. The donor base station adaptation layer entity may transfer thedata to the associated PDCP entity based on the UE bearer identifier andlogical channel identification information (or radio beareridentification information) included in the received data.

As another method, in the case where the first hop IAB nodedifferentiates the per-UE radio bearer data via the GTP TEID andtransfers the same to the donor base station as shown in FIGS. 15 to 17,the IAB 2 node may separately transmit the per-UE radio bearers usingthe donor base station IP address and the GTP TEID mapped to the UE'sRLC entity (or RLC configuration information). The IAB 1 node may addthe TEID and donor base station IP address for the user data (e.g., IPpacket) to the header via the radio bearer per UE on the adaptationlayer and transmit the same. The adaptation layer of the IAB 2 node mayassociate the TEID and donor base station IP address to the logicalchannel identification information of the transmit RLC entity andtransmit the same. As an example, the donor base station mayindicate/configure, in the IAB 2 node, the mapping information betweenthe TEID mapped to the specific radio bearer/RLC bearer of the specificUE and the logical channel identification information (or radio beareridentification information) on the radio interface between IAB 2 and thedonor base station. The information may be included and provided in theadaptation layer configuration information on the RRC message for IAB 2radio resource configuration. Or, the information may be included andprovided in the RLC configuration information on the RRC message for IAB2 radio resource configuration. Or, the information may be included andprovided in the logical channel configuration information on the RRCmessage for IAB 2 radio resource configuration. Or, the information maybe included and provided in the F3AP message between the donor basestation and the IAB 2 node. The configuration information/mappinginformation may include the UE identifier, the TEID associated with theUE's radio bearer identifier/logical channel identification information,donor base station IP address and logical channel identificationinformation (or radio bearer identification information) for the RLCbearer on the radio interface between IAB 2 and the donor base stationmapped thereto. The mapping information may be indicated from the donorbase station to the IAB 2 node via an RRC message or F3AP message. Thedonor base station may indicate, via the F3AP message, the configurationinformation including the mapping information corresponding to the IABnode 2 upon indicating the RRC message to the UE to configure the radioresource in the UE.

Protocol Structure Embodiment for L2 Forwarding by IAB Node-2(Adaptation Layer Lower than RLC is Applied)

As another example, if the adaptation layer is configured between theMAC and RLC layers (or the adaptation function is provided using the MACheader on the MAC layer) as shown in FIG. 19, the per-UE radio bearerfor uplink data needs to be mapped to the radio bearer/RLC bearer on theinterface between IAB nodes or the radio bearer/RLC bearer between theIAB node and the donor base station at the adaptation layer entity ofthe first hop IAB node (IAB 1) having a direct radio connection with theUE. The number of RLC entities (RLC bearers) on the interface betweenIAB nodes or the number of RLC entities (or RLC bearers) between the IABnode and the donor base station may be set to be identical to the numberof per-UE, per-radio bearer RLC entities (per-UE RLC bearers) of the IAB1 node. For example, the IAB 1 node is connected with UE-1 and UE-2, andtwo radio bearers are configured in UE-1, and three radio bearers areconfigured in UE-2. No UE is directly connected to the IAB 2 node, andno other IAB node than IAB 1 is directly connected to IAB 2. Where no UEis directly connected to the donor base station, and no other IAB nodethan IAB 2 is directly connected thereto, the number of RLC entities inUE 1 for uplink data processing is two, and the number of RLC entitiesin UE 2 is three. The number of receive RLC entities of the IAB 1 nodereceiving data from UE 1 and UE 2 is the sum of 2 and 3, i.e., 5. Thenumber of transmit RLC entities from the IAB 1 node to the IAB 2 node isfive as well. The number of receive RLC entities of the IAB 2 node isfive. The number of transmit RLC entities from the IAB 2 node to thedonor base station is five, and the number of receive RLC entities ofthe donor base station is five. Each interface has the same number ofRLC bearers.

If an adaptation layer is configured between the MAC and RLC layers (orif the adaptation function is provided using the MAC header on the MAClayer), the UE and the donor base station have a PDCP entity per radiobearer and, for regular radio bearers, not duplicate bearers, the PDCPentities and the RLC entities are mapped in a one-to-one manner. Thus,the same number of RLC entities as the number of radio bearers betweenthe UE and the base station need to be configured in the IAB node aswell.

Therefore, the IAB node may multiplex and transmit the MAC SDUsbelonging to different radio bearers (or belonging to different logicalchannels) in one UE via the same transmission channel on the interfacebetween IAB nodes or on the interface between the IAB node and the donorbase station.

The IAB node may multiplex and transmit the MAC SDUs of different UEsvia the same transmission channel on the interface between IAB nodes oron the interface between the IAB node and the donor base station.

The IAB node may multiplex and transmit the MAC SDUs belonging todifferent radio bearers (or belonging to different logical channels) ofdifferent UEs via the same transmission channel on the interface betweenIAB nodes or on the interface between the IAB node and the donor basestation.

As an example, the transmit adaptation layer entity adds the headerincluding the UE identifier (UE ID) and radio bearer identificationinformation (data radio bearer identification information or SRBidentification information)/logical channel identification informationfor the data (e.g., RLC PDU) received from the RLC entity (radio bearer)configured per UE per radio bearer. The transmit adaptation entity maytransfer the header-added data to the transmit MAC entity, and thetransmit MAC entity may add the logical channel identificationinformation associated therewith to the MAC header using one or morepieces of information of the UE identifier (UE ID) and radio beareridentification information/logical channel identification information.The MAC header-added message may be multiplexed and transmitted via thesame transmission channel on the interface between the IAB node and thedonor base station or on the interface between IAB nodes. The receiveMAC entity may identify the logical channel identification informationassociated therewith, using one or more pieces of information of the UEidentifier (UE ID) and radio bearer identification information/logicalchannel identification information and separately process per-UE,per-radio bearer data. After processing the received data, the receiveMAC entity transfers the processed data to the receive adaptation layerentity. The receive adaptation layer entity transfers the data (RLC PDU)to the receive RLC entity (after removing the adaptation header) mappedto the UE identifier and radio bearer identifier/logical channelidentification information.

As another example, in the case where the MAC entity provides a transmitadaptation layer function, the transmit MAC entity adds the header fieldincluding the UE identifier (UE ID) for the data (e.g., RLC PDU)received from the RLC entity configured per UE, per radio bearer.Further, the transmit MAC entity adds the logical channel identificationinformation associated therewith to the MAC header using one or morepieces of information of the UE identifier (UE ID) and radio beareridentification information (data radio bearer identification informationor SRB identification information)/logical channel identificationinformation. This may be multiplexed and transmitted via the sametransmission channel on the interface between the IAB node and the donorbase station or on the interface between IAB nodes. The receive MACentity may separately process per-UE, per-radio bearer data, via thelogical channel identification information associated therewith, usingone or more pieces of information of the UE identifier (UE ID) and radiobearer identification information/logical channel identificationinformation. After processing the received data, the receive MAC entitytransfers the data (RLC PDU) to the receive RLC entity (after removingthe adaptation header) mapped to the UE identifier and radio beareridentifier/logical channel identification information.

There is a limit to the maximum number of radio bearers currentlyprovidable between the UE and the base station. For example, the maximumnumber of DRBs providable is eight in LTE. In NR, the maximum number ofDRBs providable is at most 32. Thus, in the case where the IAB nodereceives multiple IAB nodes and the UE and relays the same to the donorbase station, if the maximum number of DRBs providable by the IAB nodeis identical to the maximum number of DRBs providable by a regular UE,such an issue may arise where the number of radio bearers and UEscapable of relaying between the IAB node and the donor base station orbetween IAB nodes is limited.

To address this, the radio bearer on the radio interface between the UEand the first hop IAB node (IAB 1) having a direct radio connection withthe UE may be mapped to the radio bearer on the radio interface betweenIAB nodes or the radio bearer between the IAB node and the donor basestation.

For example, assumes the following scenario.

The IAB 1 node is connected to UE-1, UE-2, and UE-3, and three radiobearers (radio bearer-1, radio bearer-2, and radio bearer-3) areconfigured in UE-1. Two radio bearers (radio bearer-a and radiobearer-b) are configured in UE-2. Two radio bearers (radio bearer-A andradio bearer-B) are configured in UE-3. No UE is directly connected tothe IAB 2 node, and no other IAB node than IAB 1 is directly connectedto IAB 2. No UE is directly connected to the donor base station, and noother IAB node than IAB 2 is directly connected thereto.

Under the above assumed scenario, for uplink data processing, the numberof transmit RLC entities of UE-1 is three, the number of transmit RLCentities of UE-2 is two, and the number of transmit RLC entities of UE 3is two. The numbers of receive RLC entities of the IAB 1 node peeredthereto are 3, 2, and 2. The donor base station may determine the numberof transmit RLC entities from the IAB 1 node to the IAB 2 node. Forexample, the number of radio bearers capable of same packet forwardingprocessing may be determined depending on the radio bearer type to beprovided per UE. As an example, if UE-1's radio bearer-1, UE-2's radiobearer-a, and UE-3's radio bearer-A are radio bearers capable of samepacket forwarding processing (e.g., default bearers of the same PDUsession or radio bearers providing the same service), the three radiobearers may be mapped to one RLC entity upon transmission from the IAB 1node to the IAB 2 node. Thus, the receive RLC entity (RLC-RX1) peered tothe transmit RLC entity (RLC-TX1) of UE-1 radio bearer-1 at the IAB 1node may be mapped to one transmit RLC entity (marked “RLC entity-11”for ease of description) to the IAB 2 node. The receive RLC entity(RLC-RXa) peered to the transmit RLC entity (RLC-TXa) of UE-2 radiobearer-a at the IAB 1 node may be mapped to the same transmit RLC entity(RLC entity-11) to the IAB 2 node. The receive RLC entity (RLC-RXA)peered to the transmit RLC entity (RLC-TXA) of UE-3 radio bearer-A atthe IAB 1 node may be mapped to the same transmit RLC entity (RLCentity-11) to the IAB 2 node.

In the UE, the RLC entity may be differentiated by the logical channelidentification information. Thus, the mapping between the RLC entity ofthe IAB 1 node peered to the RLC entity of the per-UE radio bearer andthe RLC entity of the IAB 1 node peered to the RLC entity of the IAB 2node may be provided by logical channel identification information. Asan example, the donor base station may provide this by configuring, inthe IAB 1 node, the mapping information between the UE's logical channelidentification information and the logical channel identificationinformation on the radio interface between the IAB 1 node and the IAB 2node.

As another method, the RLC entity in the UE may be differentiated by theradio bearer identification information associated with the PDCP entity.As an example, the donor base station may provide this by configuring,in the IAB 1 node, the mapping information between the UE's radio beareridentification information and the logical channel identificationinformation on the radio interface between the IAB 1 node and the IAB 2node. This may be indicated from the donor base station to the IAB 1node via the RRC message. The donor base station may indicate, via theF3AP message, the configuration information including the mappinginformation corresponding to the IAB node 1 upon indicating the RRCmessage so as to configure the radio resource in the UE.

As an example, the donor base station adaptation layer entity maytransfer the data to the associated RLC entity based on the UEidentifier and logical channel identification information (or radiobearer identification information) included in the received data. Asanother example, the adaptation layer may buffer/store/process dataseparately per RLC bearer/radio bearer/logical channel identificationinformation, so that the receive adaptation layer may transfer the sameto the associated RLC bearer per UE.

In a similar manner to the above-described method, there is a method ofconfiguring information for mapping the RLC bearer on the interfacebetween IAB nodes (between IAB 1 and IAB 2) (or per-UE RLC bearers atthe IAB node (IAB 2) positioned in the middle) to the RLC bearer betweenthe IAB node and the donor base station (between IAB 2 and DgNB).

Upon uplink data transmission, the RLC entities (or RLC configurationinformation) in the UE may be differentiated by the logical channelidentification information. Thus, the mapping information forinstructing to transmit data belonging to the specific radio bearer/RLCbearer of the specific UE from the IAB node to a next hop IAB node (orthe donor base station if the next hop is the donor base station) may beprovided via the logical channel identification information. As anexample, the donor base station may provide the same by configuring, inthe IAB 2 node, the mapping information between the logical channelidentification information of the specific radio bearer/RLC bearer ofthe specific UE and the logical channel identification information ofthe RLC bearer on the radio interface between the IAB 2 node and thedonor base station. This may be indicated from the donor base station tothe IAB 2 node via an RRC message or F3AP message. Or, the donor basestation may indicate, via the F3AP message, the configurationinformation including the mapping information corresponding to the IABnode upon indicating the RRC message to the UE so as to configure theradio resource in the UE.

As another method, the RLC entity in the UE may be differentiated by theradio bearer identification information associated with the PDCP entity.As an example, the donor base station may provide the radio beareridentification information by configuring, in the IAB 1 node, themapping information between the radio bearer identification informationof the specific radio bearer/RLC bearer of the specific UE and thelogical channel identification information (or radio beareridentification information) on the radio interface between IAB 1 and IAB2.

This may be included and provided in the adaptation layer configurationinformation. The configuration information/mapping information mayinclude the UE identifier, or the UE's radio bearer identifier/logicalchannel identification information, and logical channel identificationinformation (or radio bearer identification information) for the RLCbearer on the radio interface between IAB 2 and the donor base stationmapped thereto. IAB 2 may transfer the data to the MAC entity accordingto the configured mapping information.

As an example, the donor base station adaptation layer entity maytransfer the data to the associated RLC entity based on the UEidentifier and logical channel identification information (or radiobearer identification information) included in the received data. Asanother example, the adaptation layer may buffer/store/process dataseparately per RLC bearer/radio bearer/logical channel identificationinformation, so that the receive adaptation layer may transfer the sameto the associated RLC bearer per UE.

As another example, this may be provided by configuring, in IAB 2, themapping information between the logical channel identificationinformation of the RLC bearer on the radio interface between IAB 1 andIAB 2 and the logical channel identification information of the RLCbearer on the radio interface between IAB 2 and the donor base station.This may be indicated from the donor base station to the IAB 2 node viathe RRC message. Or, when this is indicated from the donor base stationto the IAB 1 node via the RRC message or when the RRC message isindicated to configure a radio resource in the UE, the configurationinformation including the mapping information corresponding to the IAB 2node may be indicated.

As another method, the RLC entity in the UE may be differentiated by theradio bearer identification information associated with the PDCP entity.As an example, the donor base station may provide the same byconfiguring, in the IAB 2 node, the mapping information between theradio bearer identification information of the RLC bearer on the radiointerface between the IAB 1 node and the IAB 2 node and the logicalchannel identification information (or radio bearer identificationinformation) on the radio interface between the IAB 2 node and the donorbase station. The IAB 2 node may add the mapping information to theheader of the data according to the configured mapping information andtransfer the header-added data to the corresponding MAC entity. Thedonor base station adaptation layer entity may transfer the data to theassociated PDCP entity based on the UE identifier and logical channelidentification information (or radio bearer identification information)included in the received data.

By applying the above-described protocol structure and RRC messageprocessing scheme, the UE may effectively configure a connection to thebase station via a multi-hop relay node under the control of the donorbase station and transmit and receive data.

A structure of a relay node capable of performing all or some of theabove-described embodiments will be briefly described again below.

FIG. 20 is a view illustrating a relay node 2000 according to anotherembodiment.

Referring to FIG. 20, a relay node 2000 processing an RRC messageincludes a controller 2010 configuring a signaling radio bearer or ahigher layer protocol connection with a donor base station, a receiver2030 receiving an RRC message transmitted from a UE, and a transmitter2020 transmitting the RRC message to the donor base station or anotherrelay node using the signaling radio bearer or the higher layerprotocol.

The controller 2010 may configure a connection with the donor basestation and configure a signaling radio bearer. Or, the controller 2010may configure a higher layer protocol connection with the donor basestation. As an example, the higher layer protocol connection may bereferred to as an F3 application protocol (F3AP).

For example, the relay node 2000 is an integrated access and backhaul(IAB) node that is connected with the UE via radio access and isconnected with another relay node or donor base station via radiobackhaul. Or, the relay node 2000 may be an IAB node connected withanother relay node or donor base station via radio backhaul. In otherwords, the relay node 2000 may be an IAB node performing directconnection via radio access with the UE or may be an IAB node that ispositioned in the middle of the relay path or on a side surface of thedonor base station and is not directly connected with the UE.

The receiver 2030 may receive mapping information from the donor basestation to configure a signaling radio bearer or higher layer protocolconnection. For example, the controller 2010 may configure a connectionusing the mapping information between the backhaul RLC channel and theUE's logical channel identification information received from the donorbase station. The configured signaling radio bearer is ciphered by thePDCP entity of the donor base station and the PDCP entity of the relaynode 2000.

Further, the receiver 2030 receives the RRC message via radio accesswith the UE.

The transmitter 2020 may add the address information for the donor basestation to the F3AP message including the RRC message and transmit thesame, by the adaptation entity of the relay node. Here, the addressinformation for the donor base station may mean a GPRS tunnelingprotocol (GTP) tunnel endpoint identifier (TEID) or a donor base stationIP address received from the donor base station.

Further, the RRC message received from the UE may be added to thepayload of the F3AP message and be transmitted via the signaling radiobearer. Besides, the F3AP message may further include at least one of UEidentification information and signaling radio bearer identificationinformation.

Accordingly, the transmitter 2020 includes the UE's RRC message in thepayload of F3AP and transfers the same to the donor base station via thesignaling radio bearer. Further, for transmission via the signalingradio bearer, the donor base station performs ciphering by the PDCPentity.

Further, the receiver 2030 may receive uplink user data from the UE inthe method of processing uplink user data.

The controller 2010 may derive a UE bearer identifier (UE-bearer-ID)using logical channel identification information associated with the RLCPDU of the uplink user data. For example, the controller 2010, uponreceiving the uplink user data, extracts the UE bearer identifier usingthe logical channel identification information associated with the RLCPDU. That is, the controller 2010 may identify the UE bearer identifierusing the logical channel identification information.

The controller 2010 may select the backhaul RLC channel for transmittinguplink user data based on at least one of the UE bearer identifier anddonor base station address information. For example, the controller 2010may select the backhaul RLC channel mapped to the UE bearer identifierusing the derived UE bearer identifier. Or, the controller 2010 mayselect the backhaul RLC channel for transmitting uplink user data usingthe donor base station address information. As an example, the donorbase station address information may be a GPRS tunneling protocol (GTP)tunnel endpoint identifier (TEID) or a donor base station IP addressreceived from the donor base station. That is, the controller 2010 maypreviously receive and store the donor base station address information.

Meanwhile, the controller 2010 may select the backhaul RLC channel basedon the backhaul RLC channel mapping information included in the UE's UEcontext setup message received from the donor base station. That is, thebackhaul RLC channel mapping information is required to select thebackhaul RLC channel using at least one of the above-described UE beareridentifier and donor base station address information. The receiver 2030may receive the backhaul RLC channel mapping information from the donorbase station.

For example, the backhaul RLC channel mapping information may include1:N (N is a natural number not less than 1) mapping information betweenthe backhaul RLC channel and at least one of the UE bearer identifierand donor base station address information. Or, the backhaul RLC channelmapping information may include mapping information between the UEbearer identifier and donor base station address information.

Meanwhile, the backhaul RLC channel may be configured according to thelogical channel configuration information of the RRC message. That is,the controller 2010 may configure the backhaul RLC channel using thelogical channel configuration information of the RRC message.

The transmitter 2020 may transmit the uplink user data to the donor basestation or another relay node via the selected backhaul RLC channel. Thetransmitter 2020 may include at least one information of the UE beareridentifier, donor base station address information, logical channelidentification information, and mapping information between the backhaulRLC channel and the logical channel identification information, in theuplink user data and transmit the same, by the adaptation entity of therelay node. For example, the controller 2010 may add UE beareridentifier information to the uplink user data in transmitting theuplink user data via the backhaul RLC channel. Adding the UE beareridentifier information may be performed by the adaptation entity of therelay node. Or, the donor base station address information and theabove-described mapping information may be included in the transmitteduplink user data so that the donor base station or another relay nodemay utilize the information.

Meanwhile, the receiver 2030 may receive an RRC connection requestmessage from the UE before receiving uplink user data from the UE.Further, the transmitter 2020 may transmit the RRC connection requestmessage to the donor base station via a signaling radio bearer or F3APmessage. Such operation step may be further included.

Besides, the controller 2010 controls the overall operation of the relaynode 2000 to include the UE's RRC message necessary to perform theabove-described embodiments in the F3AP message and transfer the samevia the SRB, and transmit the UE's uplink user data via the backhaul RLCchannel using the logical channel identification information.

The transmitter 2020 and the receiver 2030 are used to transmit orreceive signals or messages or data necessary for performing theabove-described disclosure, with the UE and another relay node or donorbase station.

The embodiments described above may be supported by the standarddocuments disclosed in at least one of the radio access systems such asIEEE 802, 3GPP, and 3GPP2. That is, the steps, configurations, andparts, which have not been described in the present embodiments, may besupported by the above-mentioned standard documents for clarifying thetechnical concept of the disclosure. In addition, all terms disclosedherein may be described by the standard documents set forth above.

The above-described embodiments may be implemented by any of variousmeans. For example, the present embodiments may be implemented ashardware, firmware, software, or a combination thereof.

In the case of implementation by hardware, the method according to thepresent embodiments may be implemented as at least one of an applicationspecific integrated circuit (ASIC), a digital signal processor (DSP), adigital signal processing device (DSPD), a programmable logic device(PLD), a field programmable gate array (FPGA), a processor, acontroller, a microcontroller, or a microprocessor.

In the case of implementation by firmware or software, the methodaccording to the present embodiments may be implemented in the form ofan apparatus, a procedure, or a function for performing the functions oroperations described above. Software code may be stored in a memoryunit, and may be driven by the processor. The memory unit may beprovided inside or outside the processor, and may exchange data with theprocessor by any of various well-known means.

In addition, the terms “system”, “processor”, “controller”, “component”,“module”, “interface”, “model”, “unit”, and the like may generally meancomputer-related entity hardware, a combination of hardware andsoftware, software, or running software. For example, theabove-described components may be, but are not limited to, a processdriven by a processor, a processor, a controller, a control processor,an entity, an execution thread, a program and/or a computer. Forexample, both the application that is running in a controller or aprocessor and the controller or the processor may be components. One ormore components may be provided in a process and/or an execution thread,and the components may be provided in a single device (e.g., a system, acomputing device, etc.), or may be distributed over two or more devices.

The above embodiments of the present disclosure have been described onlyfor illustrative purposes, and those skilled in the art will appreciatethat various modifications and changes may be made thereto withoutdeparting from the scope and spirit of the disclosure. Further, theembodiments of the disclosure are not intended to limit, but areintended to illustrate the technical idea of the disclosure, andtherefore the scope of the technical idea of the disclosure is notlimited by these embodiments. The scope of the present disclosure shallbe construed on the basis of the accompanying claims in such a mannerthat all of the technical ideas included within the scope equivalent tothe claims belong to the present disclosure.

CROSS-REFERENCE TO RELATED APPLICATION

This application claims priority to Korean Patent Application Nos.10-2018-0018672, filed on Feb. 14, 2018, and 10-2019-0009663, filed onJan. 25, 2019, under 35 U,S.C. § 119(a), in the Korean IntellectualProperty Office, the disclosures of which are incorporated by referenceherein in their entireties.

1-18. (canceled)
 19. A method for processing an radio resource control(RRC) message by a relay node, the method comprising: configuring one ofa signaling radio bearer and a higher layer protocol connection with adonor base station; receiving an RRC message transmitted from a userequipment (UE); and transmitting the RRC message to one of the donorbase station and another relay node using one the signaling radio bearerand the higher layer protocol.
 20. The method of claim 19, wherein therelay node is an integrated access backhaul (IAB) node connected withthe UE via radio access and connected with one of the another relay nodeand the donor base station via radio backhaul.
 21. The method of claim19, wherein the relay node selects the another relay node to transmitthe RRC message based on system information transmitted by one of thedonor base station and the another relay node.
 22. The method of claim19, wherein the RRC message is transmitted to the donor base station byusing the higher layer protocol through a backhaul radio link control(RLC) channel selected based on backhaul RLC channel mappinginformation.
 23. The method of claim 22, wherein the backhaul RLCchannel mapping information includes backhaul RLC channel mappinginformation for each control plane traffic type and is received in an UEcontext setup message of the UE.
 24. The method of claim 19, wherein thetransmitting the RRC message includes adding address information for thedonor base station to an F3AP message including the RRC message by anadaptation entity of the relay node and transmitting the same.
 25. Themethod of claim 24, wherein the address information for the donor basestation is a general packet radio service (GPRS) tunneling protocol(GTP) tunnel endpoint identifier (TEID) or a donor base station IPaddress received from the donor base station.
 26. The method of claim19, wherein the RRC message is added to a payload of an F3 applicationprotocol (F3AP) message and is transmitted via the signaling radiobearer.
 27. The method of claim 26, wherein the F3AP message furtherincludes at least one of UE identification information andidentification information for the signaling radio bearer.
 28. A relaynode processing an radio resource control (RRC) message, the relay nodecomprising: a controller configuring one of a signaling radio bearer anda higher layer protocol connection with a donor base station; a receiverreceiving an RRC message transmitted from a UE; and a transmittertransmitting the RRC message to one of the donor base station andanother relay node using one of the signaling radio bearer and thehigher layer protocol.
 29. The relay node of claim 28, wherein the relaynode is an integrated access backhaul (IAB) node connected with the UEvia radio access and connected with one of the another relay node andthe donor base station via radio backhaul.
 30. The relay node of claim28, wherein the controller selects the another relay node to transmitthe RRC message based on system information transmitted by the donorbase station or the another relay node.
 31. The relay node of claim 28,wherein the RRC message is transmitted to the donor base station byusing the higher layer protocol through a backhaul radio link control(RLC) channel selected based on backhaul RLC channel mappinginformation.
 32. The relay node of claim 31, wherein the backhaul RLCchannel mapping information includes backhaul RLC channel mappinginformation for each control plane traffic type and is received in an UEcontext setup message of the UE.
 33. The relay node of claim 28, whereinthe transmitter adds address information for the donor base station toan F3AP message including the RRC message by an adaptation entity of therelay node and transmits the same.
 34. The relay node of claim 33,wherein the address information for the donor base station is a generalpacket radio service (GPRS) tunneling protocol (GTP) tunnel endpointidentifier (TEID) or a donor base station IP address received from thedonor base station.
 35. The relay node of claim 28, wherein the RRCmessage is added to a payload of an F3AP message and is transmitted viathe signaling radio bearer.
 36. The relay node of claim 35, wherein theF3AP message further includes at least one of UE identificationinformation and identification information for the signaling radiobearer.